“Do not consider the merits of individuals, but the office of the priests. Or, if you look at the merits, consider the priest as Elijah. Look upon the merits of Peter also, or of Paul, who handed down to us this mystery which they had received of the Lord Jesus (Matt. 26:26-28, Mark 14:22-24, Luke 22:19-20, 1 Cor. 11:23-25). Consider not the bodily forms, but the grace of the Mysteries*. Believe that the Lord Jesus is present at the invocation of the priest…” (St. Ambrose, Bishop of Milan, 374-397)
St. Ambrose: “Perhaps you will say, ‘I see something else, how is it that you say I receive the Body of Christ?’ First of all, the Apostle taught you to, “look not to the things that are seen but to the things that are unseen; for the things that are seen are transient, but the things that are unseen are eternal (2 Cor. 4:18).”
“…Let us prove that this is not what nature made, but what the blessing consecrated, and that the power of blessing is greater than that of nature, because by blessing nature itself is changed.
“Moses was holding a rod, he cast it down and it became a serpent. Again, he took hold of the tail of the serpent and it returned to the nature of a rod (Ex. 4:3, 4). You see that by virtue of the prophetic office there were two changes, of the nature both of the serpent and of the rod. …The people of the fathers thirsted, Moses touched the rock and water flowed out of the rock (Ex. 17:6). Did not grace work a result contrary to nature, so that the rock poured forth water, which by nature it did not contain? Marah was a most bitter stream, so that the thirsting people could not drink. Moses cast wood into the water and the water lost its bitterness, which grace suddenly tempered (Ex. 15:25). In the time of Elisha the prophet, one of the sons of the prophets lost the head from his axe, which sank. He who had lost the iron asked Elisha, who cast in a piece of wood and the iron swam (2 Kings 6:3-6). This, too, we clearly recognize as having happened contrary to nature, for iron is of heavier nature than water.
“We see, then, that grace has more power than nature, and yet so far we have only spoken of the grace of a prophet’s blessing. If the blessing of man had such power as to change nature, what are we to say of that Divine consecration where the very words of the Lord and Saviour operate? For that sacrament which you receive is made what it is by the word of Christ. If the word of Elijah had such power as to bring down fire from heaven (1 Kings 18:37-39), shall not the word of Christ have power to change the nature of the elements? You read concerning the making of the whole world: ‘He spoke and they were made, He commanded and they were created (Ps. 33:9 LXX**).’ Shall not the word of Christ, which was able to create out of nothing that which never existed, be able to change things which already exist into what they were not? For it is no less to give a new nature to things than to change them.
“Let us use the example… of the Incarnation to prove the truth of the mystery. Did the course of nature proceed as usual when the Lord Jesus was born of Mary? Why do you seek the order of nature in the Body of Christ, seeing that the Lord Jesus Himself was born of a Virgin, not according to nature? It is the true Flesh of Christ which was crucified and buried, this then is truly the Sacrament of His Body.
“The Lord Jesus Himself proclaims: ‘This is My Body (Matt. 26:26).’ Before the blessing of the heavenly words another nature is spoken of, after the consecration the Body is signified. He Himself speaks of His Blood, [‘this is My blood of the covenant] (Matt. 26:28).’ Before the consecration it has another name, after it is called Blood; and when partaking you say, Amen; that is, It is true. Let the heart within confess what the mouth utters, let the soul feel what the voice speaks.” (St. Ambrose, excerpts from Concerning the Mysteries, Chapters 2, 3, 5 & 9. Presented during Lent with a possible date of 387 A.D.)
* Mysteries: The name Mysteries was that by which the sacraments were commonly known in the Early Church. The word Mysteries is still used in the eastern Orthodox Churches and is the equivalent of our word Sacraments. St. Ambrose uses the words interchangeably.
** LXX: Septuagint, the Greek translation of the Old Testament which was the primary Scripture of the early Church and Fathers.