Confession of sin

If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness. 1 John 1:9

In the church you shall acknowledge your transgressions, and you shall not come near for your prayer with an evil conscience. This is the way of life. Didache (A.D. 80-140) ch.4

For it is good for a man to make confession of his trespasses rather than to harden his heart, as the heart of those was hardened who made sedition against Moses the servant of God; whose condemnation was clearly manifest, for they went down to hades alive, and death shall be their shepherd. Clement of Rome (A.D. 96) ch. 50

But every Lord's day gather yourselves together, and break bread, and give thanksgiving after having confessed your transgressions, that your sacrifice may be pure. But let no one who is at odds with his fellow come together with you, until they be reconciled, that your sacrifice may not be profaned. Didache (A.D. 80-140) ch.14

"Hermas, make an end of constantly entreating for your sins; entreat also for righteousness, that you may take some part forthwith to your family." Hermas (A.D. 150) ch. 12

"Born again, not of blood, nor of the will of the flesh,"… consists in repenting by not giving way to the same fault. For frequent repentance and readiness to change easily from want of training, is the practice of sin again. The frequent asking of forgiveness, then, for those things in which we often transgress, is the semblance of repentance, not repentance itself. Clement of Alexandria (A.D. 195) Ante-Nicene Fathers vol.2 pg.361

Confession is the beginning of glory, not the full desert of the crown; nor does it perfect our praise, but it initiates our dignity; and since it is written, “He that endures to the end, the same shall be saved,” whatever has been before the end is a step by which we ascend to the summit of salvation, not a terminus wherein the full result of the ascent is already gained. He is a confessor; but after confession his peril is greater, because the adversary is more provoked. Cyprian (A.D. 250) Ante-Nicene Fathers vol.5 pg.428