1 John 1:9
If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.
In order for us to walk day by day in fellowship with God, we must confess our sin. Only when sin is confessed, can we be cleansed from all unrighteousness by God. Our part is to confess our sin, so that God can do His part, cleanse us from it.