It is Written

Numbers 5:5-7 The Lord spoke to Moses, saying, "Speak to the children of Israel: 'When a man or woman commits any sin that men commit, so as to trespass against the Lord, and that soul is guilty; then he shall confess his sin which he has done, and he shall make restitution for his guilt in full, and add to it the fifth part of it, and give it to him in respect of whom he has been guilty.

Matthew 3:6 They were baptized by him in the Jordan, confessing their sins.

Matthew 5:23-24 If therefore you are offering your gift at the altar, and there remember that your brother has anything against you, leave your gift there before the altar, and go your way. First be reconciled to your brother, and then come and offer your gift.

Acts 19:18 Many also of those who had believed came, confessing, and declaring their deeds.