Chapter 18 — Part II: The Sacraments — The Holy Eucharist
Section 53. Thus the words, this is the chalice, are found in St. Luke and in the Apostle; but the words that immediately follow, of my blood, or my blood of the new testament, which shall be shed for you and for many to the remission of sins, are found partly in St. Luke and partly in St. Matthew. But the words, eternal, and the mystery of faith, have been taught us by holy tradition, the interpreter and keeper of Catholic truth.