What does someone repent of, when he has not sinned?

The lusts of the flesh is the lusts of the flesh - not the lusts of believers abiding in Jesus and partaking of the divine nature. Sinful flesh tempts believers from within to satisfy innocent and legitimate needs in sinful ways. For example, the flesh tempts believers to overindulge. Instead of overindulging, believers are temperate.

3. The Body
The body is our internal organs. It is where our appetites and passions reside and originate. Appetite has to do with food and drink, whereas passion is the seat of our emotions. As our body reacts to internal and external stimuli it produces innocent and legitimate needs which are communicated as electrical impulses.

"Our foes are within and without. We are assailed by temptations which are numerous and deceiving, the more perilous because not always clearly discerned. Often Satan conquers us by our natural inclinations and appetites. These were divinely appointed, and when given to man, were pure and holy. It was God’s design that reason should rule the appetites, and that they should minister to our happiness. And when they are regulated and controlled by a sanctified reason, they are holiness unto the Lord.

"But men’s natural appetites have been perverted by indulgence. Through unholy gratification they have become “fleshly lusts, which war against the soul.” Unless the Christian watches unto prayer, he gives loose reign to habits which should be overcome. Unless he feels the need of constant watching, ceaseless vigilance, his inclinations, abused and misguided, will be the means of his backsliding from God." (14 MR 294, 295)

"You are of that age when the will, the appetite, and the passions clamor for indulgence. God has implanted these in your nature for high and holy purposes. It is not necessary that they should become a curse to you by being debased. They will become this only when you refuse to submit to the control of reason and conscience." (3T 84)

"Christ came to bring to man moral power that he may be victorious in overcoming temptations on the point of appetite, and break the chain of the slavery of habit and indulgence of perverted appetite and stand forth in moral power as a man, and the record of heaven accredits him in its books as a man in the sight of God." (TE 264)

4. The Flesh
The flesh intercepts the innocent and legitimate needs produced by our body and converts them into unholy thoughts and feelings. For example, “I’m hungry”, is translated as, “Eat this and that”, without reference to truth or temperance. Our flesh has, as it were, a mind and voice of its own, which we must learn to disown as the voice of Satan. It generates and communicates unholy thoughts and feelings and will continue to do so until Jesus returns and replaces it with a sinless body and flesh. “Human nature is ever struggling for expression, ready for contest ...” (MB 15) “The voice and passions must be crucified.” (TSB 98)

Possessing sinful flesh, however, is not a sin. Sinning is a matter of choice and character. We do not become accountable for our inherited sinful propensities until we desire them or act them out. The sinful thoughts and feelings produced by fallen flesh are nothing more than perverted legitimate needs that must be brought under the control of a sanctified mind and will.

"The lower passions have their seat in the body and work through it. The words “flesh” or “fleshly” or “carnal lusts” embrace the lower, corrupt nature; the flesh of itself cannot act contrary to the will of God. We are commanded to crucify the flesh, with the affections and lusts. How shall we do it? Shall we inflict pain on the body? No; but put to death the temptation to sin. The corrupt thought is to be expelled. Every thought is to be brought into captivity to Jesus Christ. All animal propensities are to be subjected to the higher powers of the soul. The love of God must reign supreme; Christ must occupy an undivided throne. Our bodies are to be regarded as His purchased possession. The members of the body are to become the instruments of righteousness." (AH 127)

"The bodies of human beings, made for the dwelling place of God, had become the habitation of demons. The senses, the nerves, the passions, the organs of men, were worked by supernatural agencies in the indulgence of the vilest lust. The very stamp of demons was impressed upon the countenances of men. Human faces reflected the expression of the legions of evil with which they were possessed." (DA 36)

Interesting observations, James. Is there a distinction between body and flesh?

James, it sounds like you believe sinful flesh nature does not tempt us from within to satisfy our innocent and legitimate needs in sinful ways. Am I hearing you right? What would happen if Jesus refused to allow evil angels to tempt us? Would we cease to sin?

1 Corinthians
10:13 There hath no temptation taken you but such as is common to man: but God [is] faithful, who will not suffer you to be tempted above that ye are able; but will with the temptation also make a way to escape, that ye may be able to bear [it].

James, there is no doubt Jesus will permit evil angels to tempt us to the very end. Thank you for pointing it out. And, thank you Jesus, we can resist them unto the honor and glory of God. I'm not clear, though, what you believe is the origin of temptations. It sounds like you are saying all temptations originate with evil angels and that sinful flesh nature does not tempt us from within. Again, if Jesus refused to allow evil angels to tempt us, would sinful flesh nature tempt us from within? Or, would temptations cease? For example, if people were sitting alone in the wilderness, could they be tempted (if Jesus refused to allow evil angels to tempt them)? If so, what would be the origin of their temptations?

PS - Please don't misunderstand my questions. If you believe sinful flesh nature does not tempt us from within that's fine; I'm not here to find fault or criticize. I am merely trying to understand what you believe.

[Whatever enters the mouth goes into the stomach and is eliminated.] But those things which proceed out of the mouth come from the [mind], and they defile a man. For out of the [mind] proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies. These are the things which defile a man, but to eat ... does not defile a man.

The lusts of the flesh is the lusts of the flesh - not the lusts of believers abiding in Jesus and partaking of the divine nature.