Chapter 12 — Part I: The Creed — Article X: The Forgiveness of Sins
Section 5. All Sins Committed After Baptism — It being necessary, therefore, that a power of forgiving sins, distinct from that of Baptism, should exist in the Church, to her were entrusted the keys of the kingdom of heaven, by which each one, if penitent, may obtain the remission of his sins, even though he were a sinner to the last day of his life. This truth is vouched for by the most unquestionable authority of the Sacred Scriptures. In St. Matthew the Lord says to Peter: I will give to thee the keys of the kingdom of heaven; and whatsoever thou shalt bind upon earth, shall be bound also in heaven; and whatsoever thou shalt loose on earth, shall be loosed also in heaven; and again: Whatsoever you shall bind upon earth, shall be bound also in heaven; and whatsoever you shall loose on earth, shall be loosed also in heaven.' Further, the testimony of St. John assures us that the Lord, breathing on the Apostles, said: Receive ye the Holy Ghost, whose sins you shall forgive they are forgiven them; and whose sins you shall retain, they are retained. '