We have already explained, in part and as far as we could understand it, the reason for His bodily appearance. No one but the Savior Himself, who in the beginning made all things from nothing, could change the corruptible into incorruption. No one but the Image of the Father could recreate in humanity what was made according to the Image. No one but our Lord Jesus Christ, who is Life itself, could raise the mortal to immortality. And no one but the Word, who orders all things and alone is the Father's true only-begotten Son, could teach about the Father and overthrow the worship of idols.
But what was owed by all also had to be paid, for, as I said before, everyone was under obligation to die; indeed, this was the chief reason He came among us. Therefore, after proving His divinity through His works, He offered the sacrifice on behalf of all, giving His own temple over to death in place of all, so that He might make everyone free from liability and from the ancient transgression. At the same time, He showed Himself stronger than death by displaying His own body incorruptible as the first-fruits of the resurrection of all.
Do not be surprised if we often say the same things about the same subjects. Since we are speaking about God’s good purpose, we explain the same thought in several ways, lest we appear to leave something out and be accused of treating the subject inadequately. It is better to accept the criticism of repetition than to omit something that ought to be written.
The body shared the common essence of all human bodies—for it was a human body. Although it was formed from a virgin alone by an unprecedented wonder, it was nevertheless mortal and, like bodies of the same kind, it died. But because the Word had come upon it, it was no longer corrupted according to its own nature. Because God the Word dwelt in it, it was placed beyond corruption.
Thus two marvels happened at once: the death of all was fulfilled in the Lord's body, while death and corruption were abolished because the Word was present in it. Death was necessary, and a death on behalf of all had to take place, so that what everyone owed might be paid.
Therefore, as I said, because the Word Himself could not die—for He was immortal—He took for Himself a body that could die, so that He might offer it as His own in place of all and, suffering on behalf of all through His presence in it, "bring to nothing the one who had the power of death, that is, the devil, and deliver those who throughout their lives were enslaved by the fear of death."