1 John 1:9

"If we confess our sins, He is faithful and just to forgive us our sins, and to purge us from all iniquity." Not only the past, but haply if we have contracted any from this life; because a man, so long as he bears the flesh, cannot but have some at any rate light sins. But these which we call light, do not thou make light of. If thou make light of them when thou weighest them, be afraid when thou countest them. Many light make one huge sin: many drops fill the river; many grains make the lump. And what hope is there? Before all, confession: lest any think himself righteous, and, before the eyes of God who seeth that which is, man, that was not and is, lift up the neck. Before all, then, confession; then, love: for of charity what is said? "Charity covereth a multitude of sins."

Now let us see whether he commendeth charity in regard of the sins which subsequently overtake us: because charity alone extinguisheth sins. Pride extinguisheth charity: therefore humility strengtheneth charity; charity extinguisheth sins. Humility goes along with confession, the humility by which we confess ourselves sinners: this is humility, not to say it with the tongue, as if only to avoid arrogancy, lest we should displease men if we should say that we are righteous. This do the ungodly and insane: "I know indeed that I am righteous, but what shall I say before men? If I shall call myself righteous, who will bear it, who tolerate? let my righteousness be known unto God: I however will say that I am a sinner, but only that I may not be found odious for arrogancy." Tell men what thou art, tell God what thou art. Because if thou tell not God what thou art, God condemneth what He shall find in thee. Wouldest thou not that He condemn thee? Condemn thou. Wouldest thou that He forgive? Do thou acknowledge, that thou mayest be able to say unto God, "Turn Thy face from my sins." Say also to Him those words in the same Psalm, "For I acknowledge mine iniquity." "If we confess our sins, He is faithful and just to forgive us our sins, and to purge us from all iniquity. If we say that we have not sinned, we make Him a liar, and His word is not in us." If thou shalt say, I have not sinned, thou makest Him a liar, while thou wishest to make thyself true. How is it possible that God should be a liar, and man true, when the Scripture saith the contrary, "Every man a liar, God alone true"? Consequently, God true through Himself, thou true through God; because through thyself, a liar.