Chapter 11 — Part I: The Creed — Article IX: The Holy Catholic Church; the Communion of Saints
Section 40. The Church is also to be called holy because she is united to her holy Head, as His body; that is, to Christ the Lord,' the fountain of all holiness, from whom flow the graces of the Holy Spirit and the riches of the divine bounty. St. Augustine, interpreting these words of the Prophet: Preserve my soul, for I am holy," thus admirably expresses himself: Let the body of Christ boldly say, let also that one man, exclaiming from the ends of the earth, boldly say, with his Head, and under his Head, I am holy; for he received the grace of holiness, the grace of Baptism and of remission of sins. And a little further on: If all Christians and all the faithful, having been baptised in Christ, have put Him on, according to these words of the Apostle: "As many of you as have been baptised in Christ, have put on Christ"; if they are made members of his body, and yet say they are not holy, they do an injury to their Head, whose members are holy.