Of the mystical feast of the altar of the Lord. Lest any should think lightly of it, St. Ambrose shows that it is of higher antiquity than the sacred rites of the Jews, since it was foreshadowed in the sacrifice of Melchisedech, and far better than the manna, as being the Body of Christ.
43. The cleansed people, rich with these adornments, hastens to the altar of Christ, saying: “I will go to the altar of God, to God Who makes glad my youth;” for having laid aside the slough of ancient error, renewed with an eagle's youth, it hastens to approach that heavenly feast. It comes, and seeing the holy altar arranged, cries out: “You have prepared a table in my sight.” David introduces the people as speaking, where he says: “The Lord feeds me, and nothing shall be wanting to me, in a place of good pasture has He placed me. He has led me forth by the water of refreshment.” And later: “For though I walk in the midst of the shadow of death, I will fear no evils, for You are with me. Your rod and Your staff have comforted me. You have prepared in my sight a table against them that trouble me. You have anointed my head with oil, and Your inebriating cup, how excellent it is!”
44. We must now pay attention, lest perchance any one seeing that what is visible (for things which are invisible cannot be seen nor comprehended by human eyes), should say, “God rained down manna and rained down quails upon the Jews,” but for the Church beloved of Him the things which He has prepared are those of which it is said: “That eye has not seen, nor ear heard, neither has it entered into the heart of man, what things God has prepared for them that love Him.” So, lest any one should say this, we will take great pains to prove that the sacraments of the Church are both more ancient than those of the synagogue, and more excellent than the manna.
45. The lesson of Genesis just read shows that they are more ancient, for the synagogue took its origin from the law of Moses. But Abraham was far earlier, who, after conquering the enemy, and recovering his own nephew, as he was enjoying his victory, was met by Melchisedech, who brought forth those things which Abraham reverently received. It was not Abraham who brought them forth, but Melchisedech, who is introduced without father, without mother, having neither beginning of days, nor ending, but like the Son of God, of Whom Paul says to the Hebrews: “that He remains a priest for ever,” Who in the Latin version is called King of righteousness and King of peace.
46. Do you recognize Who that is? Can a man be king of righteousness, when himself he can hardly be righteous? Can he be king of peace, when he can hardly be peaceable? He it is Who is without mother according to His Godhead, for He was begotten of God the Father, of one substance with the Father; without a father according to His Incarnation, for He was born of a Virgin; having neither beginning nor end, for He is the beginning and end of all things, the first and the last. The sacrament, then, which you received is the gift not of man but of God, brought forth by Him Who blessed Abraham the father of faith, whose grace and deeds we admire.
47. We have proved the sacraments of the Church to be the more ancient, now recognize that they are superior. In very truth it is a marvellous thing that God rained manna on the fathers, and fed them with daily food from heaven; so that it is said, “So man ate angels' food.” But yet all those who ate that food died in the wilderness, but that food which you receive, that living Bread which came down from heaven, furnishes the substance of eternal life; and whosoever shall eat of this Bread shall never die, and it is the Body of Christ.
49. Now consider whether the bread of angels be more excellent or the Flesh of Christ, which is indeed the body of life. That manna came from heaven, this is above the heavens; that was of heaven, this is of the Lord of the heavens; that was liable to corruption, if kept a second day, this is far from all corruption, for whosoever shall taste it holily shall not be able to feel corruption. For them water flowed from the rock, for you Blood flowed from Christ; water satisfied them for a time, the Blood satiates you for eternity. The Jew drinks and thirsts again, you after drinking will be beyond the power of thirsting; that was in a shadow, this is in truth.
49. If that which you so wonder at is but shadow, how great must that be whose very shadow you wonder at. See now what happened in the case of the fathers was shadow: “They drank, it is said, of that Rock that followed them, and that Rock was Christ. But with many of them God was not well pleased, for they were overthrown in the wilderness. Now these things were done in a figure concerning us.” You recognize now which are the more excellent, for light is better than shadow, truth than a figure, the Body of its Giver than the manna from heaven.
Source: On the Mysteries (New Advent)