It was when he gave the Holy Spirit to his apostles that the risen Christ conferred on them his own power to forgive sins: “Receive the Holy Spirit. If you forgive the sins of any, they are forgiven; if you retain the sins of any, they are retained.” (John 20:22-23) – Catechism of the Catholic Church #976
…Baptism is the first and chief sacrament of forgiveness of sins… – Catechism of the Catholic Church #977
Symbols of the Sacrament of Reconciliation:
Additional Resources:
Catechism of the Catholic Church Article 10 (paragraphs 976-987)
Small Catholic 