The Gospels provide numerous examples of Christ’s mission to forgive sins. When a paralytic was lowered through the roof of a house and placed at his feet, Christ first forgave the man’s sins and then cured his affliction (cf. Lk 5:17-26). When a sinful woman knelt at his feet in the house of Simon the Pharisee, Jesus forgave her sins because she had “loved much,” unlike the Pharisee, who had little insight into his own sinfulness (cf. Lk 7:36-50). Christ ’s parable of the prodigal son illustrates the sublime meaning of his earthly ministry, which is to forgive sins, reconcile people to God, and lead us to true happiness (cf. Lk 15:11-32).
Jesus died on the Cross and rose from the dead to reconcile sinful people with God through the forgiveness of sins and the gift of new life with the Triune God. Even on the Cross, he forgave those who were killing him and had mercy on the repentant thief.
Only God can forgive our sins. But Jesus willed that the Church should be his instrument of forgiveness on earth. On Easter night the Risen Christ imparted to his Apostles his own power to forgive sins. He breathed on them, imparting the promised Holy Spirit, and said, “Peace be with you.” Jesus was actually filling them with peace that is rooted in friendship with God. But he did more. He shared with them his own merciful mission. He breathed on them a second time and said,
As the Father has sent me, so I send you. . . . Receive the Holy Spirit. Whose sins you forgive are forgiven them, and whose sins you retain are retained. (Jn20:21-23)
That night Jesus gave the Church the ministry of the forgiveness of sins through the Apostles (cf. CCC, no. 1461). By the Sacrament of Holy Orders, bishops and priests continue this ministry to forgive sins “in the name of the Father, and of the Son, and of the Holy Spirit.” In this Sacrament, the priest acts in the person of Christ, the Head of the Church, to reconcile the sinner to both God and the Church. “When he celebrates the Sacrament of Penance, the priest is fulfilling the ministry of the Good Shepherd who seeks the lost sheep. . . . The priest is the sign and instrument of God’s merciful love for the sinner” (CCC, no. 1465).
The Sacrament of Penance involves a conversion of our hearts to God, a confession of sins to a priest, the forgiveness of our sins, a penance to make some amends for sin, and reconciliation with God and the Church. For those who commit mortal sin after Baptism, this Sacrament is necessary for being reconciled to God and the Church.