Catechism Part 1, Section 2, Chapter 3, Article 10: The Forgiveness of Sins (976-987)

The forgiveness of sins is associated not only with the Holy Spirit, but with the Church and communion of saints. The Church received the power to forgive sins from Christ through the Holy Spirit.

I. One baptism for the forgiveness of sins (977-980)
Baptism is the first sacrament of forgiveness of sins because it unites us with Christ. However, this does not completely keep people from sinning, so the Church must continue to forgive sins of the faithful, through the sacrament of penance, to reconcile believers to God.

II. The Power of the Keys (981-987)
The apostles carry out the ministry of repentance and forgiveness.With out the forgiveness of sins there is no hope in life to come or eternal liberation. The Church's ministry is to forgive sins and reconcile men to God. They have the keys to heaven. The Church must forgive all offenses, no matter how serious. Forgiveness of sins is linked to faith in the Holy Spirit given to us by Christ who rose from the dead, and the Church has the power to forgive sins through baptism and penance.