Origen of Alexandria

That bread which God the Word confesses to be his own body is the Word that nourishes souls, the Word proceeding from God, the very bread that comes from the living bread which is set out upon our table of which was written: “Thou preparest a table before me in the presence of my enemies.” That drink which God the Word confesses to be his blood is the Word that gives refreshment and exhilarates the heart.… This drink is the fruit of the true vine, the blood of that grape cast in the winepress of the passion. So also the bread is the word of Christ made from that corn which, falling onto the good ground, brought forth much fruit. He was not speaking of the visible bread alone which he was holding in his hands as he called it his body. It is the word in the mystery of which that bread was to be broken. Nor did he call that visible drink as such his blood, but the word in the mystery of which that drink was to be poured out. For to what else could the body and blood of the Lord refer other than the atoning Word that nourishes and gladdens the heart? Why did he not say, “This is my bread of the New Testament” just as he said, “This is my blood of the New Testament?” Because the bread is the word of righteousness, by the eating of which souls are nourished. The drink is the word of knowledge of Christ according to the mystery of his birth and passion.

Why does the Evangelist make mention here of “birth,” whereas at the start of the Gospel he had said “generation”? For in this place he says, “Now the birth of Jesus Christ took place in this way,” but there “The book of the generation.” … What then is the difference between “birth” and “generation”? How are either of them to be understood as applied to Christ? Note that this, my spoken word, in its own proper nature, is intangible and invisible. But when it is written down in a book, in a manner of speaking, it takes on a body. It is then both seen and touched. So it is with the fleshless, bodiless Word of God. The Word is neither seen nor described according to his Godhood but becomes, through his incarnation, subject to both sight and description. For this reason there is the “book” of his “generation” as of one who is made flesh. But here the point under investigation is not why he says “book” instead of “vision” or “account” (for this has been discussed already). Rather, it is why, when Matthew had previously mentioned “generation,” he here speaks of “birth.” What is “birth” as distinguished from “generation”?
There is a difference between generation and birth. For “generation,” or “coming into being,” is the original formation of things by God, while “birth” is the succession from others caused by the verdict of death that came on account of the transgression. And even now, “generation” has something incorruptible and sinless about it, whereas “birth” implies that which is subject to passion and sin. The Lord in his eternal generation is incapable of sin. His being born did not undermine his eternal generation, which is incorruptible. But upon being born he assumed what is passible. That does not imply that he assumed what is subject to sin. He continued to bear the original Adam incapable of being lessened, either in respect of corruptibility or as regards the possibility of sin. Hence the “generation” in the case of Christ is not according to some procession from nonbeing into being. It is rather a transition [a path, a way] from existing “in the form of God” to the taking on of “the form of a servant.” Hence his “birth” was both like ours and above ours. For to be born “of woman” is like our birth, but to be born “not of the will of the flesh” or “of man” but of the Holy Spirit is above ours. There is here an intimation, a prior announcement of a future birth to be bestowed on us by the Spirit.