If you look into church history you will find what is called the Disciplina Arcani or Discipline of the Secret or Discipline of the Arcane, which was a restriction imposing silence upon Christians with respect to their rites and doctrines. It was a theological term used to describe the 'tradition' or custom which came in and prevailed in the church, whereby knowledge of the more 'intimate mysteries' of the Christian religion was carefully kept from non-Christians and even from those who were undergoing instruction in the faith. The true origin of these 'mysteries' came from the oral teachings from Greek and Hellenistic sources which formed the basis of this secret oral tradition, which in the 4th century came to be called the disciplina arcani. It appears that it contained liturgical details and certain other ancient customs which remain a part of Christianity, for example, the doctrine of Transubstantiation is thought to have been a part of this. So lets look below the surface and see what this "Discipline" actually is from several sources.

Disciplina Arcani: A Latin phrase, meaning discipline of the secret and referring to a practice of the early Church, especially during the Roman persecutions, to: (1) conceal Christian truths from those who, it was feared, would misinterpret, ridicule and profane the teachings, and persecute Christians for believing them; (2) instruct catechumens in a gradual manner, withholding the teaching of certain doctrines until the catechumens proved themselves of good faith and sufficient understanding.
http://www.osv.com/OSV4MeNav/CatholicAl ... fault.aspx, Our Sunday Visitor's Catholic Almanac: Glossary D-M, “Disciplina Arcani”:

This term signifies in general that which is unknowable, or valuable knowledge that is kept secret. In pagan antiquity the word mystery was used to designate certain esoteric doctrines, such as Pythagoreanism, or certain ceremonies that were performed in private or whose meaning was known only to the initiated, e.g., the Eleusinian rites, Phallic (penis) worship. In the language of the early Christians the mysteries were those religious teachings that were carefully guarded from the knowledge of the profane (see DISCIPLINE OF THE SECRET).

..theological term used to express the custom which prevailed in the earliest ages of the Church, by which the knowledge of the more intimate mysteries of the Christian religion was carefully kept from the heathen and even from those who were undergoing instruction in the Faith. The custom itself is beyond dispute.
CATHOLIC ENCYCLOPEDIA: Discipline of the Secret (Catholic Encyclopedia), Discipline of the Secret (Latin Disciplina Arcani ):

There are many other "unwritten mysteries of the Church," says St. Basilc. 66 and 67). They are not mentioned in the Scripture. But they are of great authority and significance. They are indispensable for the preservation of right faith. They are effective means of witness and communication. According to St. Basil, they come from a "silent" and "private" tradition: [From the silent and mystical tradition, from the unpublic and ineffable teaching]. This "silent" and "mystical" tradition, "which has not been made public," is not an esoteric doctrine, reserved for some particular elite. The "elite" was the Church. In fact, "tradition" to which St. Basil appeals, is the liturgical practice of the Church. St. Basil is referring here to what is now denoted as disciplina arcani [The discipline of secrecy].
[Cf. Hermann Dörries, De Spiritu Sancto, Der Beitrag des Basilius zum Abschluss des trinitarischen Dogmas (Göttingen, 1956); J. A. Jungmann, S.J., Die Stellung Christi im liturgischen Gebet, 2. Auflage (Münster i/W, 1962), ss. 155 ff., 163 ff.; Dom David Amand, L’ascese monastique de Saint Basile, Editions de Maredsous (1949), pp. 75-85. The footnotes in the critical editions of the treatise De Spiritu S. by C. F. H. Johnson (Oxford, 1892) and by Benoit Pruche, O.P. (in the ‘Sources Chrètiennes,’ Paris, 1945) are highly instructive and helpful. On disciplina arcani see O. Perler, s.v. Arkandisciplin, in ‘Reallexikon für Antike and Christentum,’ Bd. I (Stuttgart, 1950), ss. 671-676,. Joachim Jeremias, Die Abendmahlsworte Jesu (Göttingen, 1949), ss. 59 ff., 78 ff., contended that disciplina arcani could be detected already in the formation of the text of the Gospels, and actually existed also in Judaism; cf. the sharp criticism of this thesis by R. P. C. Hanson, Tradition in the Early Church (London, 1962), pp. 27 ss].


So is this a Christian belief or direction from the Apostles that should be in the church, it appears not. Does it have any scriptural support or sanction, it appears to fail on that point. So where it come from, and why was it allowed into the church. Lets take a look...

So where did these traditions, rites, and practices come from, if not from scripture, then where. We look in history and we find many of these came from the from ancient 'Mystery Religions', so lets dig down and focus on the origin of these 'Mysteries' and see what we find. It seems that many corruptions from Greek mythology and Hellenistic philosophy and other non Christian sources such as Gnosticism came into the early church and this included the ancient 'Mysteries'. So lets see what these were..

...The cults of the mystery religions were influenced uniformly by the ideas of the Greek philosophers. A few of them existed before the turn of the Era, but several more appeared at about the turn of the Era. They reached their height of popularity during the times of early Christianity. Christianity was born during a period of proliferation. Christianity itself in the beginning consisted of many cults that existed independently and had very diverse doctrines. Because of such diversity, it is debatable whether Gnosticism was just another cult of Christianity or whether it was a separate religion.

The following features were common to all mystery religions. Admission to the community was by a rite of initiation, a solemn consecration. The initiation was held in secret, which explains why they were called "mysteries."... Esoteric Christianity: The Greek Mystery Religions and Their Impact on Christianity

Now the problem was that many Christians leaders were influenced or had picked up the pagan 'Mysteries' and mixed it with Christianity. Clement of Alexandria stated that “what was taught in the Mysteries concerned the universe, and was the completion and perfection of all instruction; wherein things were seen as they were, and nature and her works were made known.”

Clement of Alexandria writings show that he was completely immersed in the pagan 'Myesteries' and are full of terminology taken directly from the language of the Pagan Mysteries. He writes of the Christian revelation as “the holy Mysteries.” , the ‘divine secrets’, ‘... Clement further states “I am become holy while I am being initiated.” Clement tells us that in early Christianity there were likewise Lesser Mysteries for beginners on the spiritual path and Greater Mysteries which were a secret higher knowledge, which led to full ‘initiation.’ ‘The secret traditions of true Gnosis,’ he explains, had been transmitted “to a small number, by a succession of masters, and not in writing.”

So then we find the following connection...

"Alexandria was, in addition, one of the chief seats of that peculiar mixed pagan and Christian speculation known as Gnosticism. Basilides and Valentinus taught there. It is no matter of surprise, therefore, to find some of the Christians affected in turn by the scientific spirit. At an uncertain date, in the latter half of the second century, "a school of oral instruction" was founded. "

Note, it mixed pagan and Christian speculation, so a combining of paganism into Christianity

So lets look closer at the 'pagan speculation' and see what we find.

'The idea of self-knowledge is central to the purpose of the ancient Mysteries. The Greek Temple of Apollo at Delphi had inscribed ‘Gnothi Seauton’ or ‘Know thy Self.’ The Gnosis[8] or knowledge which initiates of the Mysteries sought and Masters taught was the knowledge of self. The Gnostic Book of Thomas stated:

“Whoever has not known himself has known nothing, but he who has known himself has at the same time already achieved Gnosis about the depth of all things.”

"This idea is extremely ancient and we may find interesting connections between our own ritual and that of the ancient Pagan[9] Mysteries of Greece, Egypt, and Persia.

The ancient Mysteries existed for the purpose of satisfying the desire of those who wished to know the nature of themselves and of their creator, their purpose in life, and what might come after life. Plato said that the object of the Mysteries was to re-establish the soul in its primitive purity, and to that state which it had lost..."

"The Mysteries demanded complete adherence to silence among its adherents."

“This demand was taken seriously in the Eleusinian Mysteries as failure to keep vows resulted in death. For this reason very little direct information exists concerning details of the Mysteries- the ritual, passwords, symbols and text."

"..More than five centuries before the arrival of Christianity, at Eleusis (a small town outside Athens) the people established the Eleusinian mysteries.There they reenacted the myth of Demeter's search and her reunion with her daughter Persephone. Every year two Eleusinian ceremonies were held: the Greater mysteries, in honor of Demeter and Kori, and the Lesser mysteries, in honor of Kori alone.

The Lesser mysteries were a preparation for the Greater ones. They were performed at Agrae on the river Ilissus (outside Athens) in the month of Anthesterion (February-March). Because of the oaths for secrecy we have sparse testimony of what exactly took place in the initiation ceremony. Something was recited, something was revealed, and acts were performed. Also, the initiates took an oath of secrecy before preparing for the Greater mysteries. The penalty for revealing the mysteries to outsiders was death. The initiates of the Lesser mysteries waited at least one year until they could participate in the Greater mysteries, which were held at Eleusis in the month of Boedromion (September-October). The Greater mysteries included baptism in the sea, three days of fasting, and the completion of the mysterious central rite. These acts completed the initiation, and the initiate was promised rewards in the life after death..."

Mithraism is an example of a "mystery religion" that flourished in the near east at that time. Mithraism took on the form of a mystery religion, with elaborate rights and ceremonies. It came into the ancient Roman world about 75 B.C. David Ulansey explains it is called such because " ..like the other ancient 'mystery religions,' such as the Eleusinian mysteries and the mysteries of Isis, the Mithraic cult maintained strict secrecy about its teachings and practices, revealing them only to initiates.

http://www.comereason.org/cmp_rlgn/c...#ixzz2c5QFcgKA

So what connection does it have in Christianity today, well lets look and see what we uncover...

"..There are four sets of "Mysteries of the Rosary" (Joyful, Luminous, Sorrowful, and Glorious). These four "Mysteries of the Rosary" therefore contain, a total of twenty mysteries. The Joyful, Luminous, Sorrowful, and Glorious Mysteries are then said on specific days of the week (see each set of mysteries below). During private recitation of the Rosary, each decade requires devout meditation on a specific mystery. Public recitation of the Rosary (two or more people), requires a leader to announce each of the mysteries before the decade, and start each prayer (see "The Family Rosary" below)."

How to Pray the Rosary

"The rosary beads provide a physical method of keeping count of the number of Hail Marys said as the mysteries are contemplated.[43] The fingers are moved along the beads as the prayers are recited. By not having to keep track of the count mentally, the mind is more able to meditate on the mysteries. A five decade rosary contains five groups of ten beads (a decade), with additional large beads before each decade.[47] The Hail Mary is said on the ten beads within a decade, while the Our Father is said on the large bead before each decade. A new mystery is meditated upon at each of the large beads. Some rosaries, particularly those used by religious orders, contain 15 decades, corresponding to the traditional 15 mysteries of the rosary. Both five and 15 decade rosaries are attached to a shorter strand, which starts with a crucifix followed by one large, three small, and one large beads before connecting to the rest of the rosary"

"Five methods of praying the rosary are presented within the works of Saint Louis de Montfort, a French Roman Catholic priest and writer of the early 18th century. Montfort was an early proponent of Mariology, and much of his work is devoted to the subjects of the Blessed Virgin Mary and the rosary. While the rosary contains a fixed set of prayers recited with the use of beads, Montfort proposed a number of methods to pray the rosary with more thorough devotion. Two of the methods are described in his book The Secret of the Rosary, in the fiftieth rose (chapter):

"In order to facilitate the exercise of the holy Rosary, here are several methods to recite it holily, with the meditation of the joyful, sorrowful and glorious mysteries of Jesus and Mary............."

And it goes on and on....

The Mysteries of the Rosary - Prayers - Catholic Online
http://www.catholic.org/prayers/mystery.php

And its not just beads that are being used, here is from the Vatican Catechism of the Catholic Church:

1378 Worship of the Eucharist. In the liturgy of the Mass we express our faith in the real presence of Christ under the species of bread and wine by, among other ways, genuflecting or bowing deeply as a sign of adoration of the Lord. "The Catholic church has always offered and still offers to the sacrament of the Eucharist the cult of adoration, not only during Mass, but also outside of it, reserving the consecrated host with the utmost care, exposing them to the solemn veneration of the faithful, and carrying them in procession."

Source: Catechism of the Catholic Church, published by Ligouri Publications, English translation © 1994 by the United States Catholic Conference, Inc.--Libreria Editrice Vaticana, bearing the Imprimi Potest of Joseph Cardinal Ratzinger, page 347.

We also find that transubstantiation was first practiced by ancient religions which had nothing to do with Christianity. The noted historian Durant said that belief in transubstantiation as practiced by the priests of the Roman Catholic system is "one of the oldest ceremonies of primitive religion." The Story Of Civilization, p. 741. The syncretism and mysticism of the Middle East were great factors in influencing the West, particularly Italy. Roman Society From Nero To Marcus Aurelius, Dill. In Egypt priests would consecrate mest cakes which were supposed to be come the flesh of Osiris. Encyclopedia Of Religions, Vol. 2, p. 76. The idea of transubstantiation was also characteristic of the religion of Mithra. “The Mysteries” are referenced or eluded to in respect to it’s various branches throughout ancient history and all of the Mysteries had a single root which appears to have been the Mysteries of Isis in Egypt. At a certain level ( or degree) the initiate was told that he would be part of a brotherhood spanning the entire world, which included the Greek Mysteries, Oriental Mysteries, the Jewish Mysteries (Kaballah) and presumably all other Mysteries so this spanned the known world, so its not picked up from any scripture or Biblical truth, it has its own origin.

So lets dig a little deeper and see what we have, lets look at the definition...

"Mystery religions, sacred mysteries or simply mysteries, were religious cults of the Greco-Roman world for which participation was reserved to initiates (mystai).[1] The main characterization of this religion is the secrecy associated with the particulars of the initiation and the cult practice, which may not be revealed to outsiders. The most famous mysteries of Greco-Roman antiquity were the Eleusinian Mysteries, which were of considerable antiquity and predated the Greek Dark Ages. The popularity of mystery cults flourished on Late Antiquity; Julian the Apostate in the mid 4th century is known to have been initiated into three distinct mystery cults—most notably the Mithraic Mysteries."

So the Mithraic Mysterys, that was picked up in the Roman Empire and blossomed. As Alexander the Great made conquests, mystery religions came with the territory. The same is true for the Roman Empire. The sun gods and goddesses including Mithra, Phrygian Cybele and the Egyptian Isis, to mention a few, were brought into the empires as annexations were made. And, of course, along with mystery religion came astrology, whose central figure is the sun.

Rome gained dominance over the Grecian Empire. At the death of Caesar Augustus,the time of Christ, the Roman empire stretched from Spain to the Caspian Sea, including Egypt, the Sinai peninsula, and Israel. Christianity was born and grew up in this setting.

The most significant aspect of the Greco-Roman civilization connection was that of religion. The Greeks and Romans worshipped numerous gods, the Romans picked up the mystery religions of the Greeks and renamed their gods. Religious ceremonies, rites and festivals were very important and many were celebrated. Notable festivals include the Greek festival of Zeus, the birthday of the Roman sun god, and the celebrations in honor of the fertility goddess at the spring equinox. The Romans also picked up and believed in the pagan god named Mithra (or Mithras). He was known, in various forms, in India, Persia, Greece, and throughout the Roman Empire. For the Greeks and Romans in the first century, Mithras was the chief figure in a mystery religion called Mithraism that held prominence in the Roman Empire. remnant of Mithraism is most evident in the Christian Eucharist, which involves the eating of the flesh and drinking of the blood of a deity(Christ). Since the drinking of blood has always been an abomination in Judaism it was not the origin of this rite, it is much more logical to attribute this ritual to Mithraism, which had a much similar ritual. It is clear that Christianity adopted aspects of Mithraism, the setting of the birthday of Christ on December 25th, which was Mithra birthday, and the shifting of the day of worship to the day of the Sun. The celebration of December 25, a tradition that began in the 4th century so it was not from the Apostles, however December 25 was the birthday of the more popular Roman god known as the "Unconquered Sun" with whom Constantine identified himself, who was closely associated with Mithras. Mithras is always described as "sol invictus" (the unconquered sun) in inscriptions.

...it is easy to understand that many of the emperors yielded to the delusion that they could unite all their subjects in the adoration of the one sun-god who combined in himself the Father-God of the Christians and the much-worshipped Mithras; thus the empire could be founded anew on unity of religion. Even Constantine, as will be shown farther on, for a time cherished this mistaken belief…it was especially in the western part of the empire that the veneration of Mithras predominated. Would it not be possible to gather all the different nationalities around his altars? Could not Sol Deus Invictus, to whom even Constantine dedicated his coins for a long time, or Sol Mithras Deus Invictus, venerated by Diocletian and Galerius, become the supreme god of the empire? Constantine may have pondered over this. Nor had he absolutely rejected the thought even after a miraculous event had strongly influenced him in favour of the God of the Christians…As pontifex maximus he watched over the heathen worship and protected its rights…It is true that the believers in Mithras also observed Sunday as well as Christmas. Consequently Constantine speaks not of the day of the Lord, but of the everlasting day of the sun.

(Herbermann, Charles, and Georg Grupp. Constantine the Great. The Catholic Encyclopedia. Vol. 4. Nihil Obstat. Remy Lafort, Censor. Imprimatur. +John M. Farley, Archbishop of New York. New York: Robert Appleton Company, 1908. 1 Sept. 2008 <http://www.newadvent.org/cathen/04295c.htm>)


So we see how this mystery religion came in under Constantine who was the Roman Emperor, and certainly a supporter of the mystery religion but presented himself as a Christian to gain their support. Here is a good explanation...

During the 1st century CE, a cult of Mithra, made much progress in Rome, after enduring persecution, when some Emperors adopted the religion... Mithra became very popular among the Roman legionaries and later even among the Emperors. The worship of Mithra was first recognized by Emperor Aurelian and he instituted the cult of "Sol Invictus" or the Invincible Sun. Emperor Diocletian also a worshipper of Mithra, the Sun God, burned much of the Christian scriptures in 307 CE

This enabled Emperor Constantine to merge the cult of Mithra with that of Christianity that was developing much. He declared himself a Christian but at the same time maintained his ties to the Mithra cult. He retained the title "Pontifus Maximus" the high priest. On his coins were inscribed: "Sol Invicto comiti" which means, commited to the invincible sun. This new blend of the two faiths, he officially proclaimed as Christianity. Christianity spread all over the Roman Empire and Eastern Europe by massive persecution and brought an end to a variety of religions that flourished there. [...]

Until the fourth century, Mithra and Christianity were distinct but after Constantine, they were blended so that the empire could unite them under a religion for both pagans and Christians.

In 313 A.D., Emperor Constantine declared December 25th to be the birthday of Jesus (December 25th was prescribed earlier as the birthday of Mithra, by emperor Aurelian). Sabbath day, which is literally Saturday (as the Jews still maintain), became Sunday as it was the day of the Sun, another element from the Mithra worship.”

Then we have the first Sunday Law enacted by Emperor Constantine - March, 321 A.D.-
On the venerable Day of the Sun let the magistrates and people residing in cities rest, and let all workshops be closed. In the country, however, persons engaged in agriculture may freely and lawfully continue their pursuits; because it often happens that another day is not so suitable for grain-sowing or for vine-planting; lest by neglecting the proper moment for such operations the bounty of heaven should be lost.(Given the 7th day of March, Crispus and Constantine being consuls each of them for the second time [A.D. 321].)
Source: Codex Justinianus, lib. 3, tit. 12, 3; trans. in Philip Schaff, History of the Christian Church, Vol. 3 (5th ed.; New York: Scribner, 1902), p. 380, note 1.

Transition from Pagan to Christian
[p. 122] This legislation by Constantine probably bore no relation to Christianity; it appears, on the contrary, that the emperor, in his capacity of Pontifex Maximus, was only adding the day of the Sun, the worship of which was then firmly [p. 123] established in the Roman Empire, to the other ferial days of the sacred calendar…
[p. 270] What began, however, as a pagan ordinance, ended as a Christian regulation; and a long series of imperial decrees, during the fourth, fifth, and sixth centuries, enjoined with increasing stringency abstinence from labour on Sunday.
Source: Hutton Webster, Rest Days, pp. 122, 123, 270. Copyright 1916 by The Macmillan Company, New York.

“It may be mentioned here that the Greeks celebrated the birthday of their sun-god Apollo at the winter solstice. Another important point is the fact that the Christian Church abandoned the Jewish sabbath (contrary to the commandment of their God) in favour of the Mithraic day of the sun.”
"Jesus Versus Christianity" by Alfred Reynolds (1993)1

It appears, from your posts, that indeed, "the ancient Mystery Religions got picked up as 'Tradition'".

Are you a historian, hobbyist historian or theologian?

...
.

History and theology are my background.

So we see at that time the cult of Mithraism or sun-worship was the official religion of the Roman Empire. It had its own organization, temples, priesthood, robes—everything. It also had an official worship day on which special homage was given to the sun. That day was called “The Venerable Day of the Sun.” It was the first day of the week, and when Constantine combined the pagans into the church they were observing the day of the sun for their adoration of the sun god. It was their special holy day. In order to make it more convenient for them to make the change to the new religion, Constantine accepted their day of worship, Sunday, instead of the Christian Sabbath which had been observed by Jesus and His disciples. At that time there was increasing anti-Jewish feelings against those who were accused of putting Jesus to death. Those feelings would naturally condition many Christians to swing away from something which was held religiously by the Jews. It is therefore easier to understand how the change was imposed on Christianity through a strong civil law issued by Constantine as the Emperor of Rome. . Those early Christians, feeling that the Jews should not be followed any more than necessary, were ready to swing away from the Sabbath which was kept by the Jews.

We find the following in church history...

Pagan Festivals and Church Policy
The Church made a sacred day of Sunday … largely because it was the weekly festival of the sun; for it was a definite Christian policy to take over the pagan festivals endeared to the people by tradition, and to give them a Christian significance.
Source: Arthur Weigall, The Paganism in Our Christianity, p. 145. Copyright 1928 by G. p. Putnam’s Sons, New York.

Church decrees Sunday sacredness-

Council of Laodicea (343-381?)
[p. 310] Can. 16.“On Saturday [Greek sabbaton,“the Sabbath”] the Gospels and other portions of the Scripture shall be read aloud.”…
[p. 316] Can. 29.“Christians shall not Judaize and be idle on Saturday, but shall work on that day; but the Lord’s day they shall especially honour, and, as being Christians, shall, if possible, do no work on that day. If, however, they are found Judaizing, they shall be shut out [Greek anathema] from Christ.”…
[p. 320] Can. 49.“During Lent, the bread shall not be offered, except on Saturday and Sunday.”…
Can. 51.“During Lent, no feast of the martyrs shall be celebrated, but the holy martyrs shall be commemorated on the Saturdays and Sundays of Lent.”
Source: Charles Joseph Hefele, A History of the Christian Councils, Vol. 2, trans. and ed. by H. N. Oxenham (Edinburgh: T. and T. Clark, 1896), pp. 310, 316, 320.

Councils of the Church enforce Sunday observance.
[p. 105] The Council of Orleans (538), while protesting [p. 106] against an excessive Sabbatarianism, forbade all field work under pain of censure; and the Council of Macon (585) laid down that the Lord’s Day ‘is the day of perpetual rest, which is suggested to us by the type of the seventh day in the law and the prophets,’ and ordered a complete cessation of all kinds of business. How far the movement had gone by the end of the 6th cent. is shown by a letter of Gregory the Great (pope 590–604) protesting against the prohibition of baths on Sunday.
Source: M. G. Glazebrook,“Sunday,” in James Hastings, ed., Encyclopedia of Religion and Ethics (New York: Scribner, 1928), Vol. 12, pp. 105, 106.

If as many suppose, Christians as a whole observed Sunday in place of the "Jewish" Sabbath from resurrection Sunday forward, then why was it necessary for the church to enact ecclesiastical laws to enforce Sunday worship as a day of rest? Simply put, the issue to the Catholic Church has always been one of authority, authority to declare binding holy festival days. It is a mark of their authority to institute such days, even appropriating previously pagan days and declaring them obligatory, and that one commits a sin if you do not attend services on those days. The Bible is quite silent on Sunday sacredness, so the "Bible Only" Protestants contradict themselves by observing it as a replacement for the Sabbath.

"Unquestionably the first law, either ecclesiastical or civil, by which the Sabbatical observance of that day is known to have been ordained, is the edict of Constantine, 321 A.D."--"Chamber's Encyclopedia," article, "Sabbath."

Here is the first Sunday Law in history, a legal enactment by Constantine 1 (reigned 306-331): "On the Venerable Day of the Sun ["venerabili die Solis"--the sacred day of the Sun] let the magistrates and people residing in cities rest, and let all workshops be closed. In the country, however, persons engaged in agriculture may freely and lawfully continue their pursuits; because it often happens that another day is not so suitable for grain-sowing or for vine-planting; lest by neglecting the proper moment for such operations the bounty of heaven should be lost--Given the 7th day of March,[A.D. 321], Crispus and Constantine being consuls each of them for the second time."--The First Sunday Law of Constantine 1, in "Codex Justinianus," lib. 3, tit. 12, 3; trans. in Phillip Schaff "History of the Christian Church," Vol. 3, p. 380.

"This [Constantine's Sunday decree of March, 321] is the 'parent' Sunday law making it a day of rest and release from labor. For from that time to the present there have been decrees about the observance of Sunday which have profoundly influenced European and American society. When the Church became a part of State under the Christian emperors, Sunday observance was enforced by civil statutes, and later when the Empire was past, the Church, in the hands of the papacy, enforced it by ecclesiastical and also by civil enactments."--Walter W. Hyde, "Paganism to Christianity in the Roman Empire," 1946, p. 261.
"Constantine's decree marked the beginning of a long, though intermittent series of imperial decrees in support of Sunday rest."-- Vincent J. Kelly, "Forbidden Sunday and Feast-Day Occupations," 1943, p. 29.

"Constantine labored at this time untiringly to unite the worshipers of the old and the new into one religion. All his laws and contrivances are aimed at promoting this amalgamation of religions. He would by all lawful and peaceable means melt together a purified heathenism and a moderated Christianity ... Of all his blending and melting together of Christianity and heathenism, none is more easy to see through than this making of his Sunday law: The Christians worshiped their Christ, the heathen their Sun-god ...[so they should now be combined."--H.G. Heggtveit, "illustreret Kirkehistorie," 1895, p. 202.

"If every Sunday is to be observed joyfully by the Christians on account of the resurrection, then every Sabbath on account of the burial is to be regarded in execration [cursing] of the Jews."--Pope Sylvester, quoted by S.R.E. Humbert, "Adversus Graecorum Calumnias," in J.P. Migne, "Patrologie," p. 143.[Sylvester (A.D. 314-337) was the pope at the time Constantine 1 was Emperor.]

"All things whatsoever that were prescribed for the [bible] Sabbath, we have transferred them to the Lord's day, as being more authoritative and more highly regarded and first in rank, and more honorable than the Jewish Sabbath."--Bishop Eusebius, quoted in J.P. Migne, "Patrologie," p. 23, 1169-1172.[Eusebius of Caesarea was a high-ranking Catholic leader during Constantine's lifetime.]

These Gentile Christians of Rome and Alexandria began calling the first day of the week 'the Lord's day.' This was not difficult for the pagans of the Roman Empire who were steeped in sun worship to accept, because they [the pagans] referred to their sun-god as their 'Lord.' "--EM. Chalmers, "How Sunday Came Into the Christian Church," p. 3.

Here is more about Constantine from The Catholic Encyclopedia:

Constantine the Great… Constantine can rightfully claim the title of Great, for he turned the history of the world into a new course and made Christianity...the religion of the State… it is easy to understand that many of the emperors yielded to the delusion that they could unite all their subjects in the adoration of the one sun-god who combined in himself the Father-God of the Christians and the much-worshipped Mithras; thus the empire could be founded anew on unity of religion. Even Constantine…cherished this mistaken belief… Could not Sol Deus Invictus, to whom even Constantine dedicated his coins for a long time, or Sol Mithras Deus Invictus, venerated by Diocletian and Galerius, become the supreme god of the empire? Constantine may have pondered over this. Nor had he absolutely rejected the thought even after a miraculous event had strongly influenced him in favour of the God of the Christians... It is true that the believers in Mithras also observed Sunday as well as Christmas. Consequently Constantine speaks not of the day of the Lord, but of the everlasting day of the sun. (Herbermann C., Georg Gp. Constantine the Great. The Catholic Encyclopedia. Vol. 4. Nihil Obstat. Remy Lafort, Censor. Imprimatur. +John M. Farley, Archbishop of New York. New York: Robert Appleton Company, 1908).
Constantine decreed circa March 7, 321:

Let all judges, the people of cities, and those employed in all trades, remain quiet on the Holy Day of Sunday. Persons residing in the country, however, can freely and lawfully proceed with the cultivation of the fields; as it frequently happens that the sowing of grain or the planting of vines cannot be deferred to a more suitable day, and by making concessions to Heaven the advantage of the time may be lost (Code of Justinian, Book III, Title XII, III. THE JUSTINIAN CODE FROM THE CORPUS JURIS CIVILIS. Translated from the original Latin by Samuel P. Scott. Central Trust Company, Cincinnati, 1932).
Shortly after the above decree, Eusebius recorded this about Constantine:

Accordingly he enjoined on all the subjects of the Roman empire to observe the Lord's day, as a day of rest (Eusebius. Life of Constantine, Book IV, Chapter 18).
Notice that "the Lord's day" became enjoined by a decree of a Roman Empire. Also notice the following:

There is a large body of civil legislation on the Sunday rest side by side with the ecclesiastical. It begins with an Edict of Constantine, the first Christian emperor, who forbade judges to sit and townspeople to work on Sunday (Slater T. Transcribed by Scott Anthony Hibbs. Sunday. The Catholic Encyclopedia, Volume XIV Copyright © 1912 by Robert Appleton Company Online Edition Copyright © 2003 by K. Knight).
The bolded quote shows one of the first official intertwinings of European politics and Catholic doctrine. Despite the fact that he was not baptized nor ordained, the influence of the sun-god worshiping Emperor Constantine, who declared himself a bishop, was highly significant:

So prominent had Christians and their day become that when the Emperor Constantine proclaimed Sun Day as the weekly holy day for all Romans, some Christians believed that it was for their sake. More likely Constantine, like many Roman aristocrats of the time, was simply trying to find common ground for his mixed pagan and Christian subjects, especially his soldiers. Unity was for the good of the state and the emperors' power (Harline C. Sunday: A History of the First Day from Babylonia to the Super Bowl. Doubleday, NY, 2007, p. 17).
However, after a time, Constantine did clearly begin to provide more favor the Roman version of Christianity which (like the pagans, but unlike the Church of God) endorsed Sunday. He, the sun-worshiping emperor, then called for the famous Council of Nicea, which took place in 325 A.D. This council decided that Sunday was to be the day of worship and that Passover was to be observed on Sunday (and that eventually became what is known as Easter). After that council, those in the Church of God who kept the Sabbath were considered to be heretics and outcasts and had to flee in the wilderness.
The Emperor authorized persecution. Around 332, Constantine issued what is known as the Edict Against the Heretics,

Victor Constantinus, Maximus Augustus, to the heretics. “Understand now, by this present statute, ye Novatians, Valentinians, Marcionites, Paulians, ye who are called Cataphrygians, and all ye who devise and support heresies by means of your private assemblies, with what a tissue of falsehood and vanity, with what destructive and venomous errors, your doctrines are inseparably interwoven; so that through you the healthy soul is stricken with disease, and the living becomes the prey of everlasting death. Ye haters and enemies of truth and life, in league with destruction! All your counsels are opposed to the truth, but familiar with deeds of baseness; full of absurdities and fictions: and by these ye frame falsehoods, oppress the innocent, and withhold the light from them that believe. Ever trespassing under the mask of godliness, ye fill all things with defilement: ye pierce the pure and guileless conscience with deadly wounds, while ye withdraw, one may almost say, the very light of day from the eyes of men. But why should I particularize, when to speak of your criminality as it deserves demands more time and leisure than I can give? For so long and unmeasured is the catalogue of your offenses, so hateful and altogether atrocious are they, that a single day would not suffice to recount them all. And, indeed, it is well to turn one’s ears and eyes from such a subject, lest by a description of each particular evil, the pure sincerity and freshness of one’s own faith be impaired. Why then do I still bear with such abounding evil; especially since this protracted clemency is the cause that some who were sound are become tainted with this pestilent disease? Why not at once strike, as it were, at the root of so great a mischief by a public manifestation of displeasure?" (Chapter LXIV.—Constantine’s Edict against the Heretics. This document is from the Christian Classics Ethereal Library at Calvin College).

Some of those referred to as Paulians (Paulicians) and Cataphrygians were part of the true Church of God; thus they would have rejected Sunday and other doctrines of the mystery religions and paganism.

The falling away had been foretold as the truth was being carried to all parts of the Roman Empire and beyond and Christians were daily being baptized as the gospel spread and the great apostasy from a power was identified in scripture, but its important to understand how it happened also. So look in scripture and let it unveil what it has:

Lets take a look at 2 Thessalonians 2:7

2 Thessalonians 2:7King James Version (KJV)
For the mystery of iniquity doth already work: only he who now letteth will let, until he be taken out of the way.

It shows.

All your sources are inaccessible to an Internet audience. It is patently obvious that you are copying and pasting, without any critical analysis or acknowledgement, but wholesale parital pieces of text of a book written for an audience in the years prior to 1990.

Such a practice is dishonest, is called plagiarism and is an indictable offense in a court of law. Is it right for a Christian to do such a thing?

.....
..

Just putting the facts and the sources, and letting the reader decide. I would suggest going into Dr. Samuele Bacchiocchi's books especially 'From Sabbath to Sunday: A Historical Investigation of the Rise of Sunday' which I asked if I could use this and his text from his books on the internet, as he was a family friend.

Here is from Samuele Bacchiocchi's book From Sabbath to Sunday in which he lays the change, ' as a result of an interplay of political, social, pagan and religious factors', I feel it can be traced more closely directly to the Babylonian system of worship, so we shall see.

"...How did the change come about from Saturday to Sunday in early Christianity? To find an answer to this question I spent five years at the Pontifical University in Rome, investigating for my doctoral dissertation the earliest Christian documents. This short article represents a brief summary of my research.

Historically, the change from Sabbath to Sunday has been attributed to the ecclesiastical authority of the Roman Catholic church rather than to Biblical or apostolic precepts. Thomas Aquinas, for example, explicitly states that:

"the observance of the Lord's Day took the place of the observance of the Sabbath not by virtue of the [Biblical] precept but by the institution of the church." (1)

Recently, however, some scholars have argued that Sunday observance has a Biblical and apostolic origin. According to these scholars, from the inceptions of the Church the Apostles themselves chose the first day of the week in place of the seventh day in order to commemorate the resurrection of Christ. (2)
My own assessment of the sources is that this thesis is wrong on two counts. First, the change from Saturday to Sunday occurred sometime after 135 A.D. as a result of an interplay of political, social, pagan and religious factors to be mentioned below. Second, the change originated in Rome and not in Jerusalem. Before submitting the reasons for my conclusions, we shall briefly examine the alleged role of Christ, of the resurrection and of the Jerusalem church in the origin of Sunday.

Jesus and the Origin of Sunday
A popular view holds that Christ by his provocative method of Sabbath keeping-which caused considerable controversy with the religious leaders of His day-intended to pave the way for the abandonment of the Sabbath and the adoption of Sunday keeping instead. This view clearly distorts the intent of Christ's controversial Sabbath activities and teachings which were clearly designed not to nullify but to clarify the divine intent of the Fourth Commandment.

Christ never conceded to have broken the Sabbath commandment. On the contrary He defended Himself and His disciples from the charge of Sabbath breaking by appealing to the Scriptures: "Have you read . . ." (Matt 12:3-5). The intent of Christ's provocative Sabbath teachings and activities was not to pave the way for Sunday keeping, but rather to show the true meaning and function of the Sabbath, namely, a day "to do good" (Matt 12:8), "to save life" (Mark 3:4), to loose people from physical and spiritual bonds (Luke 13:16), and to show "mercy" rather than religiosity (Matt 12:7).

The Resurrection and the Origin of Sunday
Did the apostles introduce Sunday keeping instead of Sabbath keeping in order to commemorate Christ's resurrection by means of the Lord's Supper celebration? This view, though popular, is devoid of Biblical and historical support. The major reasons, briefly stated are the following.

No Command of Christ or of the Apostles
The New Testament never suggests or commands to celebrate Christ's resurrection by a weekly or annual Sunday celebration. This silence is noteworthy in view of the specific instructions given by Christ regarding such practices as baptism (Matt 28:19-20), the Lord's Supper (Mark 14:24-25; 1 Cor 11:23-26) and foot-washing (John 13:14-15).
If Jesus wanted the day of his resurrection to be observed as a day of rest and worship, would He not told the women and the disciples when He rose: "Come apart and celebrate My Resurrection?" Instead He told the women "Go and tell my brethren to go to Galilee" (Matt 28:10) and to the disciples "Go . . . make disciples . . . baptizing them" (Matt 28:19).None of the utterances of the risen Savior reveal an intent to memorialize His resurrection by making Sunday the new day of rest and worship.

No Designation of Sunday as Day of the Resurrection
Sunday is never called in the New Testament as "Day of the Resurrection." It is consistently called "First day of the week." The references to Sunday as day of the resurrection first appear in the early part of the fourth century. (3) By that time Sunday had become associated with the resurrection....."

"....The Earliest Reference to Sunday
The earliest explicit references to Sunday keeping are found in the writings of Barnabas (about 135 A.D.) and Justin Martyr (about 150 A.D.). Both writers do mention the resurrection as a basis for Sunday observance but only as the second of two reasons, important but not predominant. Barnabas' first theological motivation for Sunday keeping is eschatological, namely, that Sunday as "the eight day" represents "the beginning of another world." (4) Justin's first reason for the Christians' Sunday assembly is the inauguration of creation: "because it is the first day on which God, transforming the darkness and prime matter, created the world." (5)
The above indications suffice to discredit the claim that Christ's resurrection on the first day of the week caused the abandonment of the Sabbath and the adoption of Sunday. The truth is that initially the resurrection was celebrated existentially rather than liturgically, that is, by a victorious way of life rather than by a special day of worship....."

".....The attachment of the Jerusalem Church to the Mosaic Law is reflected in some of the decisions of the first Jerusalem Council held about 49-50 A.D. (See Acts 15). The exemption from circumcision is there granted only "to brethren who are of the Gentiles" (Acts 15:23). No concession is made for Jewish-Christians, who must continue to circumcise their children. Moreover, of the four provisions made applicable by the Jerusalem Council to Gentiles, one is moral (abstention from "unchastity") but three are ceremonial (even Gentile Christians are ordered to abstain "from contact with idols and from [eating] what has been strangled and from [eating] blood" (Acts 15:20). This concern of the Jerusalem Council for ritual defilement and Jewish food laws reflects its continued attachment to Jewish ceremonial law and its commands. It would be unthinkable that this Church at this early time would change the Sabbath to Sunday.
James' statement at the Jerusalem Council in support of his proposal to exempt Gentiles from circumcision but not from Mosaic laws in general, is also significant: "For generations past Moses has had spokesmen in every city; he is read every Sabbath in the synagogues" (Acts 15:21). All interpreters recognize that both in his proposal and in its justification, James reaffirms the binding nature of the Mosaic Law which was customarily taught every Sabbath in the synagogue.

Paul's Last Visit
Further insight is provided by Paul's last visit to Jerusalem. The Apostle was informed by James and the elders that thousand of converted Jews were "all zealous for the Law" (Acts 21:20). The same leaders then pressured Paul to prove to the people that he also "lived in observance of the law" (Acts 21-24), by undergoing a rite of purification at the Temple. In the light of this deep commitment to the observance of the Law, it is hardly conceivable that the Jerusalem Church would have abrogated one of its chief precepts-Sabbath keeping-and pioneered Sunday worship instead.

Did Sunday Originate After 70 A.D.?
The foregoing evidences has led some scholars to argue for the Palestinian origin of Sunday observance at a slightly later time, namely, after the Roman destruction of the Temple in 70 A.D. (8) They presume that the flight of the Christians from Jerusalem to Pella as well as the psychological impact of the destruction of the Temple weaned Palestinian Christians away from Jewish observances such as Sabbath keeping.
This assumption is discredited by both Eusebius and Epiphanius who inform us that the Jerusalem Church after 70 A.D. and until Hadrian's siege of Jerusalem in 135 A.D., was composed of and administered by converted Jews, characterized as "zealous to insist on the literal observance of the Law." (9) The orthodox Palestinian Jewish-Christian sect of the Nazarenes, who most scholars regard as "the very direct descendants of the primitive community" (10) of Jerusalem, retained Sabbath keeping on Saturday until the fourth century. Indeed, seventh-day Sabbath keeping was regarded as one of this Church's distinguishing characteristics. (11) This implies that Sabbath observance was not only the traditional custom of the Jerusalem Church, but also of Palestinian Jewish-Christians long after 70 A.D.
Of all the Christian Churches, the Jerusalem Church was both ethnically and theologically the closest and most loyal to Jewish religious traditions, and thus the least likely to change the day of the Sabbath....."