In order that no one through observing the outward part should waver in faith, many instances are brought forward wherein the outward nature has been changed, and so it is proved that bread is made the true body of Christ. The treatise then is brought to a termination with certain remarks as to the effects of the sacrament, the disposition of the recipients, and such like.
50. Perhaps you will say, “I see something else, how is it that you assert that I receive the Body of Christ?” And this is the point which remains for us to prove. And what evidence shall we make use of? Let us prove that this is not what nature made, but what the blessing consecrated, and the power of blessing is greater than that of nature, because by blessing nature itself is changed.
51. 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. 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 streams of Egypt were running with a pure flow of water; of a sudden from the veins of the sources blood began to burst forth, and none could drink of the river. Again, at the prophet's prayer the blood ceased, and the nature of water returned. The people of the Hebrews were shut in on every side, hemmed in on the one hand by the Egyptians, on the other by the sea; Moses lifted up his rod, the water divided and hardened like walls, and a way for the feet appeared between the waves. Jordan being turned back, returned, contrary to nature, to the source of its stream. Is it not clear that the nature of the waves of the sea and of the river stream was changed? The people of the fathers thirsted, Moses touched the rock, and water flowed out of the rock. 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 of a sudden tempered. 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. This, too, we clearly recognize as having happened contrary to nature, for iron is of heavier nature than water.
52. We observe, then, that grace has more power than nature, and yet so far we have only spoken of the grace of a prophet's blessing. But 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. But if the word of Elijah had such power as to bring down fire from heaven, 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.” Shall not the word of Christ, which was able to make out of nothing that which was not, be able to change things which already are into what they were not? For it is not less to give a new nature to things than to change them.
53. But why make use of arguments? Let us use the examples He gives, and by the example of the Incarnation prove the truth of the mystery. Did the course of nature proceed as usual when the Lord Jesus was born of Mary? If we look to the usual course, a woman ordinarily conceives after connection with a man. And this body which we make is that which was born of the Virgin. 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 crucified and buried, this is then truly the Sacrament of His Body.
54. The Lord Jesus Himself proclaims: “This is My Body.” 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. Before the consecration it has another name, after it is called Blood. And 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.
55. Christ, then, feeds His Church with these sacraments, by means of which the substance of the soul is strengthened, and seeing the continual progress of her grace, He rightly says to her: “How comely are your breasts, my sister, my spouse, how comely they are made by wine, and the smell of your garments is above all spices. A dropping honeycomb are your lips, my spouse, honey and milk are under your tongue, and the smell of your garments is as the smell of Lebanon. A garden enclosed is my sister, my spouse, a garden enclosed, a fountain sealed.” By which He signifies that the mystery ought to remain sealed up with you, that it be not violated by the deeds of an evil life, and pollution of chastity, that it be not made known to thou, for whom it is not fitting, nor by garrulous talkativeness it be spread abroad among unbelievers. Your guardianship of the faith ought therefore to be good, that integrity of life and silence may endure unblemished.
56. For which reason, too, the Church, guarding the depth of the heavenly mysteries, repels the furious storms of wind, and calls to her the sweetness of the grace of spring, and knowing that her garden cannot displease Christ, invites the Bridegroom, saying: “Arise, O north wind, and come, thou south; blow upon my garden, and let my ointments flow down. Let my Brother come down to His garden, and eat the fruit of His trees.” For it has good trees and fruitful, which have dipped their roots in the water of the sacred spring, and with fresh growth have shot forth into good fruits, so as now not to be cut with the axe of the prophet, but to abound with the fruitfulness of the Gospel.
57. Lastly, the Lord also, delighted with their fertility, answers: “I have entered into My garden, My sister, My spouse; I have gathered My myrrh with My spices, I have eaten My meat with My honey, I have drunk My drink with My milk.” Understand, you faithful, why He spoke of meat and drink. And there is no doubt that He Himself eats and drinks in us, as you have read that He says that in our persons He is in prison.
58. Wherefore, too, the Church, beholding so great grace, exhorts her sons and her friends to come together to the sacraments, saying: “Eat, my friends, and drink and be inebriated, my brother.” What we eat and what we drink the Holy Spirit has elsewhere made plain by the prophet, saying, “Taste and see that the Lord is good, blessed is the man that hopes in Him.” In that sacrament is Christ, because it is the Body of Christ, it is therefore not bodily food but spiritual. Whence the Apostle says of its type: “Our fathers ate spiritual food and drank spiritual drink,” for the Body of God is a spiritual body; the Body of Christ is the Body of the Divine Spirit, for the Spirit is Christ, as we read: “The Spirit before our face is Christ the Lord.” And in the Epistle of Peter we read: “Christ died for us.” Lastly, that food strengthens our heart, and that drink “makes glad the heart of man,” as the prophet has recorded.
Source: On the Mysteries (New Advent)