“Only God forgives sins. Since he is the Son of God, Jesus says of himself, “The Son of Man has authority on earth to forgive sins” and exercises this divine power: “Your sins are forgiven.” Further, by virtue of his divine authority, he gives this power to men to exercise in his name. Christ has willed that in her prayer and life and action his whole Church should be the sign and instrument of the forgiveness and reconciliation that he acquired for us at the price of his blood. But he entrusted the exercise of the power of absolution to the apostolic ministry which he charged with the “ministry of reconciliation.”CCC 1441-1442
Although Christ secured our justification and redemption from sin once and for all on the cross, our sanctification requires our own participation with His redeeming actions. “If we confess our sins, he is faithful and just and will forgive our sins and cleanse us from all unrighteousness” (1 John 1:9). Since he would not always be with the Church visibly, Christ gave this power to others to act in His place and thus to continue His presence throughout time.
The means by which Jesus chose to have us confess our sins after baptism is the sacrament of Reconciliation.
It’s not surprising that, on the very day he rose from the dead, Jesus chose to institute the sacrament. In John’s gospel, we read that,
“Jesus came and stood in the midst and said to them, ‘Peace be to you!’ And when he had said this he showed them his hands and his side. The disciples, therefore, rejoiced at the sight of the Lord. He, therefore, said to them again, ‘Peace be to you! As the Father has sent Me, I also send you.’ When he had said this, he breathed upon them, and said to them, ‘Receive the Holy Spirit; whose sins you shall forgive, they are forgiven them; and whose sins you shall retain, they are retained.’”
The sacrament of Reconciliation is a sacrament in which the priest, as the agent of Jesus Christ, forgives sins when the sinner is heartily sorry for them, sincerely confesses them, and is willing to make satisfaction for them.