Jesus Christ instituted the sacrament of penance as the normative way to forgive sins.
Biblical basis as follows:
Jn 20:21-23 Jesus said to them again, “Peace be with you. As the Father has sent me,
even so I send you.” And when he had said this, he breathed on them, and
said to them, “Receive the Holy Spirit. If you forgive the sins of any, they
are forgiven; if you retain the sins of any, they are retained”
Acts 19:18 St. Luke writes, “Many also of those who were now believers came,
confessing and divulging their practices” before the apostles.
Mt 9:8 St. Matthew writes, God “had given such authority to men”
(Jesus entrusted the forgiveness of sins to His apostles and their
successors, as men)
1Jn 1:9 “If we confess our sins, he is faithful and just, and will forgive sins and
cleanse us from all unrighteousness”
2Cor 5:18 St. Paul wrote to discribe this priestly gift, God “gave us the ministry of
reconciliation”
James 5:16 “Therefore, confess your sins to one another, and pray for one another,
that you may be healed.”
Leviticus 5:5-6 says that a man guilty of sin, “shall confess the sin he has committed…
and the priest shall make atonement for him for his sin.”
Numbers 5:7 the Lord tells Moses that if anyone in Israel commits sin, “he shall confess
his sin which he has committed, and he shall make full restitution for his
wrong.”
Nehemiah 9:2-3 we see that the Israelites “stood and confessed their sins and the
inequities of their fathers” orally in the Temple where they also read the
book of the Law.
Baruch 1:13-14 the people who “have sinned against the Lord our God” are again
instructed “to make your confessions in the house of the Lord.”
Sir 4:26 “Do not be ashamed to confess your sins, and do not try to stop the
current of a river”