From the Incarnation of the Logos – St. Athanasius
For this purpose, then, the incorporeal and incorruptible and immaterial Word of God comes to our realm, howbeit he was not far from us Acts 17:27 before. For no part of Creation is left void of Him: He has filled all things everywhere, remaining present with His own Father. But He comes in condescension to show loving-kindness upon us, and to visit us.
And seeing the race of rational creatures in the way to perish, and death reigning over them by corruption; seeing, too, that the threat against transgression gave a firm hold to the corruption which was upon us, and that it was monstrous that before the law was fulfilled it should fall through: seeing, once more, the unseemliness of what had come to pass: that the things whereof He Himself was Artificer were passing away: seeing, further, the exceeding wickedness of men, and how little by little they had increased it to an intolerable pitch against themselves: and seeing, lastly, how all men were under penalty of death: He took pity on our race, and had mercy on our infirmity, and condescended to our corruption, and, unable to bear that death should have the mastery— lest the creature should perish, and His Father's handiwork in men be spent for naught— He takes unto Himself a body, and that of no different sort from ours.
For He did not simply will to become embodied, or will merely to appear. For if He willed merely to appear, He was able to affect His divine appearance by some other and higher means as well. But He takesa body of our kind, and not merely so, but from a spotless and stainless virgin, knowing not a man, a body clean and in very truth pure from intercourse of men. For being Himself mighty, and Artificer of everything, He prepares the body in the Virgin as a temple unto Himself, and makes it His very own as an instrument, in it manifested, and in it dwelling.
And thus taking from our bodies one of like nature, because all were under penalty of the corruption of death He gave it over to death in the stead of all, and offered it to the Father— doing this, moreover, of His loving-kindness, to the end that, firstly, all being held to have died in Him, the law involving the ruin of men might be undone (inasmuch as its power was fully spent in the Lord's body, and had no longer holding-ground against men, his peers), and that, secondly, whereas men had turned toward corruption, He might turn them again toward incorruption, and quicken them from death by the appropriation of His body and by the grace of the Resurrection, banishing death from them like straw from the fire.
For the Word, perceiving that no otherwise could the corruption of men be undone save by death as a necessary condition, while it was impossible for the Word to suffer death, being immortal, and Son of the Father; to this end He takes to Himself a body capable of death, that it, by partaking of the Word Who is above all, might be worthy to die in the stead of all, and might, because of the Word which had come to dwell in it, remain incorruptible, and that thenceforth corruption might be stayed from all by the Grace of the Resurrection. Whence, by offering untodeath the body He Himself had taken, as an offering and sacrifice free from any stain, straightway He put away death from all His peers by the offering of an equivalent.
For by the sacrifice of His own body, He both put an end to the law which was against us, and made a new beginning of life for us, by the hope of resurrection which He has given us. For since from man it was that death prevailed over men, for this cause conversely, by the Word of God being made man has come about the destruction of death and the resurrection of life; as the man which bore Christ says: For since by man came death, by man came also the resurrection of the dead. For as in Adam all die, so also in Christ shall all be made alive: and so forth. For no longer now do we die as subject to condemnation; but as men who rise from the dead we await the general resurrection of all, which 1 Timothy 6:15 in its own times He shall show, even God, Who has also wrought it, and bestowed it upon us.
What then was God to do? Or what was to be done save the renewing of that which was in God's image, so that by it men might once more be able to know Him? But how could this have come to pass save by the presence of the very Image of God, our Lord Jesus Christ? For by men's means it was impossible, since they are but made after an image; nor by angels either, for not even they are (God's) images. Whence the Word of God came in His own person, that, as He was the Image of the Father, He might be able to create afresh the man after the image.