John tells the account that Jesus came to the feast of tabernacles on the last day of that great feast and called the people to come to Him and drink of that living water. (See John 7:2,10,37-38}

To understand consider the ceremony of that feast. On the feast of Tabernacles the Jewish people were remembering the wilderness journey and how God brought them to the promised land.

On the last day the priest would take a special container and go to the pool of Siloam to draw a pitcher of water, with much singing and marching around the altar (7 times) the water would be poured on the altar as the people remember the water that flowed from the rock, and also showed gratitude for rain.
Also, as water was poured out, the people would pray for rain for the coming season.

Into this setting Jesus appears and cries out:
"If any man thirst, let him come to me and drink"

In chapter 6, John recorded the words of Jesus as He presented Himself as the “true bread” from heaven.
During the wilderness journey God had provided physical bread for Israel, He now offers “true bread from heaven,” offering eternal life.
In chapter 7, Jesus presents Himself at the Feast of Tabernacles as the life giving water. In the wilderness the smitten rock, produced water.

At a feast celebrating God's life giving care during their wilderness journey. Jesus announces that He is the source of the water of life. All who would come to Him in faith are welcomed to partake of Him.

He is the source of revival from spiritual draught and death that ends in physical death. Only as we partake of Him can we be revived to spiritual life that ends in eternal physical life.

The pouring of the water is also symbolic of the outpouring of the Holy Spirit.
As the first century people prayed for rain during their ceremony, so we need to pray for the outpouring of the Holy Spirit!

The next verse (John 7:39) "This spake He of the Spirit, which they that believe on Him should receive: for the Holy Spirit was not yet poured out because Jesus was not yet glorified ."

Verse 38 reads: "He that believes on Me,..out of His belly shall flow rivers of living water."

We need the Holy Spirit for revival, the Spirit that testifies of Jesus and truth, and quickens our spiritual nature thus reviving and reforming us and causing us to spread that living water to others.