(from The Discourse on the Resurrection, c. 300 A.D.)
Since flesh was made to border on incorruption and corruption, being itself neither the one nor the other, and was overcome by corruption for the sake of pleasure, though it was the work of property of incorruption; therefore it became corruptible, and was laid in the dust of the earth. When, then, it was overcome by corruption, and delivered over to death through disobedience, God did not leave it to corruption, to be triumphed over as an inheritance; but, after conquering death by the resurrection, delivered it again to incorruption, in order that corruption might not receive the property of incorruption, but incorruption that of corruption. Therefore, the apostle answers thus, “For this corruptible must put on incorruption, and this mortal must put on immortality” (1 Cor. xv. 53).
Now, the corruptible and putting on of immortality, what else is it but that which is “sown in corruption, and raised in incorruption” (1 Cor. xv. 42)–for the soul is not corruptible or mortal; but this which is mortal and corrupting is of flesh,–in order that, “as we have borne the image of the earthy, we shall also bear the image of the heavenly” (1 Cor. xv. 49). For the image of the earthy which have borne is this, “Dust thou art, and unto dust shalt thou return” (Gen. iii. 19). But the image of the heavenly is the resurrection from the dead, and incorruption; in order that “as Christ was raised up from the dead by the glory of the Father, so we also should walk in newness of life” (Rom. vi. 4).
But if anyone were to think that the earthly image is the flesh itself, but the heavenly image some other spiritual body besides the flesh; let him first consider that Christ, the heavenly man, when He appeared, bore the same form of limbs and the same image of flesh as ours, through which also He, who was not man, became man, that “as in Adam all die, even so in Christ shall all be made alive” (1 Cor. xv. 22). For if He bore flesh for any other reason than that of setting the flesh free, and raising it up, why did He bear flesh superfluously, as He purposed neither to save it, nor to raise it up? But the Son of God does nothing superfluously. He did not then take the form of a servant uselessly, but to raise it up and save it. For He was truly made man, and died, and not in mere appearance, but that He might truly be shown to be the first begotten from the dead, changing the earthy into the heavenly, and the mortal into the immortal.