1. Repentance means "a change of mind; to think differently; to reconsider."
When an unbeliever has a change of mind wrought in them by God, so that they do no longer trust in their own works, religion, efforts, merit, etc., for their salvation, but trust completely in Christ only and His finished work on Calvary for their salvation.
This is a change of mind that is repentance. "Therefore leaving the principles of the doctrine of Christ, let us go on unto perfection; not laying again the foundation of repentance from dead works,
and of faith toward God," (Hebrews 6:1).
2. Repentance at salvation is not turning from all of our sins - for that would be works.
No unbeliever has the power to turn from their sins. No unbeliever can possibly know all of their sins so thy can turn from them. "For we know that the law is spiritual: but I am carnal, sold under sin." (Romans 7:14). "For all have sinned, and come short of the glory of God;" (Romans 3:23). "For there is not a just man upon earth, that doeth good, and sinneth not." (Ecclesiastes 7:20). "Behold, thou hast made my days as an handbreadth; and mine age is
as nothing before thee: verily every man at his best state is altogether vanity. Selah." (Psalms 39:5).
3. God repents, therefore repentance is not turning from our sins, for God has never sinned.
"And it repented the LORD that he had made man on the earth, and it grieved him at his heart." (Genesis 6:6). "And the LORD repented of the evil which he thought to do unto his people." (Exodus 32:14). "And when the LORD raised them up judges, then the LORD was with the judge, and delivered them out of the hand of their enemies all the days of the judge: for it repented the LORD because of their groanings by reason of them that oppressed them and vexed them." (Judges 2:18). "And Samuel came no more to see Saul until the day of his death: nevertheless Samuel mourned for Saul: and the LORD repented that he had made Saul king over Israel." (1 Samuel 15:35). "And when the angel stretched out his hand upon Jerusalem to destroy it, the LORD repented him of the evil, and said to the angel that destroyed the people, It is enough: stay now thine hand. And the angel of the LORD was by the threshingplace
of Araunah the Jebusite." (2 Samuel 24:16).
4. Repentance is from ignorance of God's righteousness.
"For they being ignorant of God's righteousness, and going about to establish their own righteousness, have not submitted themselves unto the righteousness of God." (Romans 10:3). See Acts 17:30, then read it in its context: Acts 17:22-31. God's command to repent dealt with their false religion and their ignorance
5. Repentance will result in a changed life.
It should be noted that a changed life is not repentance, just the product of it. "For as he thinketh in his heart, so is he: ..." (Proverbs 23:7). Repentance is a change of mind and a man's thinking will change his being. An evidence of repentance is a transformed life, but a transformed life is not repentance. "Therefore if any man be in Christ, he is a new creature: old things are passed away; behold,all things are become new." (2 Corinthians 5:17).
6. Sorrow for sin will work true repentance in an unbeliever at true salvation.
This often results in an immediate turning from some sins. Other sins seem to be struggles all life long. "For godly sorrow worketh repentance to salvation not to be repented of: but the sorrow of the world worketh death." (2 Corinthians 7:10). This is the work of the Holy Ghost. "And when he is come, he will reprove the world of sin, and of righteousness, and of judgment: Of sin, because they believe not on me;" (John 16:8-9). What sin? The sin of rejecting Christ!
Note: Turning from sin is a good work of someone who is already saved. "For if ye live after the flesh, ye shall die: but if ye through the Spirit do mortify the deeds of the body, ye shall live." (Romans 8:13). This is the work of progressive sanctification in the believer. Sometimes sorrow for sins at salvation is so great it results in an immediate change in certain areas of that person's life. That is a product of repentance.