St. Thomas Aquinas
“The Evangelists did not intend to hand down the forms of the sacraments, which in the primitive Church had to be kept concealed, as Dionysius observes at the close of his book on the ecclesiastical hierarchy; their object was to write the story of Christ. Nevertheless nearly all these words can be culled from various passages of the Scriptures. Because the words, ‘This is the chalice,’ are found in Lk. 22:20, and 1 Cor. 11:25, while Matthew says in chapter 26:28: ‘This is My blood of the New Testament, which shall be shed for many unto the remission of sins.’ The words added, namely, ‘eternal’ and ‘mystery of faith,’ were handed down to the Church by the apostles, who received them from our Lord, according to 1 Cor. 11:23: ‘I have received of the Lord that which also I delivered unto you.'”
Source: St. Thomas Aquinas, Summa Theologica