Bible Reading: A root of sacrament of Penance

Why Catholics believe in the sacrament of Penance and Reconciliation

One helpful passage from the Old Testament showing its valid roots in the Jewish Law

Sirach 34: 23-26
If one man builds up and another tears down, what do they gain but trouble? If one man prays and another curses, whose voice will the Lord hear? If a man again touches a corpse after he has bathed, what did he gain by the purification? So with a man who fasts for his sins, but then goes and commits them again: Who will hear his prayer, and what has he gained by his mortification?

Jesus Christ is the purification, the fasting mortification. Humankind is widely known to be the ones who "touch the corpse after bathing" and "commits them again (sins)." So long as there are sins committed there is need for purification and mortification by touching back to Jesus Christ in the sacrament and striving not to sin again, but being humble in the knowledge that it happens more than most admit.