The following comes from Pope Innocent III, Letter Cum Marthae circa to Archbishop John of Lyon, November 29, 1202:
782 You have asked who has added to the words of the formula used by Christ
himself when he transubstantiated the bread and wine into his Body and Blood
the words that are found in the canon of the Mass generally used by the Church
but that none of the evangelists has recorded. . . . Namely, in the canon of
the Mass, we find the words “Mystery of faith” inserted into the words of
Christ. . . .
Surely there are many words and deeds of the Lord that have been omitted
in the Gospels; of these were read that the apostles have supplemented them by
their words and expressed them in their actions. . . .
But in the words that are the object of our inquiry, Brother, namely,
the words “Mystery of faith”, some have thought to find support for their
error; they say that in the sacrament of the altar it is not the reality of the
Body and Blood of Christ that is <there> but only an image, an appearance,
a symbol, since Scripture sometimes mentions that was is received at the altar
is sacrament, mystery, figure. These people fall into such error because they
neither understand correctly the testimony of the Scriptures nor receive
respectfully the divine sacraments, ignorant of both the Scriptures and the
power of God [cf. Mt 22:29]. . . .
Yet, the expression “Mystery of faith” is used, because here is that is
believed differs from what is seen, and what is seen differs from what is
believed. For what is seen is the appearance of bread and wine, and what is
believed is the reality of the flesh and blood of Christ and the power of unity
and love. (Heinrich Denzinger, Compendium of Creeds, Definitions, and
Declarations on Matters of Faith and Morals, ed. Peter Hünermann, Robert
Fastiggi, and Anne Englund Nash [43rd ed; San Francisco: Ignatius Press, 2012],
258-59)
Similarly, Thomas Aquinas noted that:
Reply Obj. 9. 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 Luke 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. (Thomas Aquinas, STh.,
III q.78 a.3 ad 9)
