Thus, then, God the Word revealed Himself to men through His works. We must next consider the end of His earthly life and the nature of His bodily death. This is, indeed, the very center of our faith, and everywhere you hear men speak of it; by it, too, no less than by His other acts, Christ is revealed as God and Son of God.
(20) We have dealt as far as circumstances and our own understanding permit with the reason for His bodily manifestation. We have seen that to change the corruptible to incorruption was proper to none other than the Savior Himself, Who in the beginning made all things out of nothing; that only the Image of the Father could re-create the likeness of the Image in men, that none save our Lord Jesus Christ could give to mortals immortality, and that only the Word Who orders all things and is alone the Father's true and sole-begotten Son could teach men about Him and abolish the worship of idols But beyond all this, there was a debt owing which must needs be paid; for, as I said before, all men were due to die. Here, then, is the second reason why the Word dwelt among us, namely that having proved His Godhead by His works, He might offer the sacrifice on behalf of all, surrendering His own temple to death in place of all, to settle man's account with death and free him from the primal transgression. In the same act also He showed Himself mightier than death, displaying His own body incorruptible as the first-fruits of the resurrection.
You must not be surprised if we repeat ourselves in dealing with this subject. We are speaking of the good pleasure of God and of the things which He in His loving wisdom thought fit to do, and it is better to put the same thing in several ways than to run the risk of leaving something out. The body of the Word, then, being a real human body, in spite of its having been uniquely formed from a virgin, was of itself mortal and, like other bodies, liable to death. But the indwelling of the Word loosed it from this natural liability, so that corruption could not touch it. Thus it happened that two opposite marvels took place at once: the death of all was consummated in the Lord's body; yet, because the Word was in it, death and corruption were in the same act utterly abolished. Death there had to be, and death for all, so that the due of all might be paid. Wherefore, the Word, as I said, being Himself incapable of death, assumed a mortal body, that He might offer it as His own in place of all, and suffering for the sake of all through His union with it, " might bring to nought Him that had the power of death, that is, the devil, and might deliver them who all their lifetime were enslaved by the fear of death." 
(21) Have no fears then. Now that the common Savior of all has died on our behalf, we who believe in Christ no longer die, as men died aforetime, in fulfillment of the threat of the law. That condemnation has come to an end; and now that, by the grace of the resurrection, corruption has been banished and done away, we are loosed from our mortal bodies in God's good time for each, so that we may obtain thereby a better resurrection. Like seeds cast into the earth, we do not perish in our dissolution, but like them shall rise again, death having been brought to nought by the grace of the Savior. That is why blessed Paul, through whom we all have surety of the resurrection, says: "This corruptible must put on incorruption and this mortal must put on immortality; but when this corruptible shall have put on incorruption and this mortal shall have put on immortality, then shall be brought to pass the saying that is written, 'Death is swallowed up in victory. O Death, where is thy sting? O Grave, where is thy victory?" 
"Well then," some people may say, "if the essential thing was that He should surrender His body to death in place of all, why did He not do so as Man privately, without going to the length of public crucifixion? Surely it would have been more suitable for Him to have laid aside His body with honor than to endure so shameful a death." But look at this argument closely, and see how merely human it is, whereas what the Savior did was truly divine and worthy of His Godhead for several reasons. The first is this. The death of men under ordinary circumstances is the result of their natural weakness. They are essentially impermanent, so after a time they fall ill and when worn out they die. But the Lord is not like that. He is not weak, He is the Power of God and Word of God and Very Life Itself. If He had died quietly in His bed like other men it would have looked as if He did so in accordance with His nature, and as though He was indeed no more than other men. But because He was Himself Word and Life and Power His body was made strong, and because the death had to be accomplished, He took the occasion of perfecting His sacrifice not from Himself, but from others. How could He fall sick, Who had healed others? Or how could that body weaken and fail by means of which others are made strong? Here, again, you may say, "Why did He not prevent death, as He did sickness?" Because it was precisely in order to be able to die that He had taken a body, and to prevent the death would have been to impede the resurrection. And as to the unsuitability of sickness for His body, as arguing weakness, you may say, "Did He then not hunger?" Yes, He hungered, because that was the property of His body, but He did not die of hunger because He Whose body hungered was the Lord. Similarly, though He died to ransom all, He did not see corruption. His body rose in perfect soundness, for it was the body of none other than the Life Himself.
(22) Someone else might say, perhaps, that it would have been better for the Lord to have avoided the designs of the Jews against Him, and so to have guarded His body from death altogether. But see how unfitting this also would have been for Him. Just as it would not have been fitting for Him to give His body to death by His own hand, being Word and being Life, so also it was not consonant with Himself that He should avoid the death inflicted by others. Rather, He pursued it to the uttermost, and in pursuance of His nature neither laid aside His body of His own accord nor escaped the plotting Jews. And this action showed no limitation or weakness in the Word; for He both waited for death in order to make an end of it, and hastened to accomplish it as an offering on behalf of all. Moreover, as it was the death of all mankind that the Savior came to accomplish, not His own, He did not lay aside His body by an individual act of dying, for to Him, as Life, this simply did not belong; but He accepted death at the hands of men, thereby completely to destroy it in His own body.
There are some further considerations which enable one to understand why the Lord's body had such an end. The supreme object of His coming was to bring about the resurrection of the body. This was to be the monument to His victory over death, the assurance to all that He had Himself conquered corruption and that their own bodies also would eventually be incorrupt; and it was in token of that and as a pledge of the future resurrection that He kept His body incorrupt. But there again, if His body had fallen sick and the Word had left it in that condition, how unfitting it would have been! Should He Who healed the bodies of others neglect to keep His own in health? How would His miracles of healing be believed, if this were so? Surely people would either laugh at Him as unable to dispel disease or else consider Him lacking in proper human feeling because He could do so, but did not.
(23) Then, again, suppose without any illness He had just concealed His body somewhere, and then suddenly reappeared and said that He had risen from the dead. He would have been regarded merely as a teller of tales, and because there was no witness of His death, nobody would believe His resurrection. Death had to precede resurrection, for there could be no resurrection without it. A secret and unwitnessed death would have left the resurrection without any proof or evidence to support it. Again, why should He die a secret death, when He proclaimed the fact of His rising openly? Why should He drive out evil spirits and heal the man blind from birth and change water into wine, all publicly, in order to convince men that He was the Word, and not also declare publicly that incorruptibility of His mortal body, so that He might Himself be believed to be the Life? And how could His disciples have had boldness in speaking of the resurrection unless they could state it as a fact that He had first died? Or how could their hearers be expected to believe their assertion, unless they themselves also had witnessed His death? For if the Pharisees at the time refused to believe and forced others to deny also, though the things had happened before their very eyes, how many excuses for unbelief would they have contrived, if it had taken place secretly? Or how could the end of death and the victory over it have been declared, had not the Lord thus challenged it before the sight of all, and by the incorruption of His body proved that henceforward it was annulled and void?
(24) There are some other possible objections that must be answered. Some might urge that, even granting the necessity of a public death for subsequent belief in the resurrection, it would surely have been better for Him to have arranged an honorable death for Himself, and so to have avoided the ignominy of the cross. But even this would have given ground for suspicion that His power over death was limited to the particular kind of death which He chose for Himself; and that again would furnish excuse for disbelieving the resurrection. Death came to His body, therefore, not from Himself but from enemy action, in order that the Savior might utterly abolish death in whatever form they offered it to Him. A generous wrestler, virile and strong, does not himself choose his antagonists, lest it should be thought that of some of them he is afraid. Rather, he lets the spectators choose them, and that all the more if these are hostile, so that he may overthrow whomsoever they match against him and thus vindicate his superior strength. Even so was it with Christ. He, the Life of all, our Lord and Savior, did not arrange the manner of his own death lest He should seem to be afraid of some other kind. No. He accepted and bore upon the cross a death inflicted by others, and those others His special enemies, a death which to them was supremely terrible and by no means to be faced; and He did this in order that, by destroying even this death, He might Himself be believed to be the Life, and the power of death be recognized as finally annulled. A marvelous and mighty paradox has thus occurred, for the death which they thought to inflict on Him as dishonor and disgrace has become the glorious monument to death's defeat. Therefore it is also, that He neither endured the death of John, who was beheaded, nor was He sawn asunder, like Isaiah: even in death He preserved His body whole and undivided, so that there should be no excuse hereafter for those who would divide the Church.
(25) So much for the objections of those outside the Church. But if any honest Christian wants to know why He suffered death on the cross and not in some other way, we answer thus: in no other way was it expedient for us, indeed the Lord offered for our sakes the one death that was supremely good. He had come to bear the curse that lay on us; and how could He "become a curse"  otherwise than by accepting the accursed death? And that death is the cross, for it is written "Cursed is every one that hangeth on tree."  Again, the death of the Lord is the ransom of all, and by it "the middle wall of partition"  is broken down and the call of the Gentiles comes about. How could He have called us if He had not been crucified, for it is only on the cross that a man dies with arms outstretched? Here, again, we see the fitness of His death and of those outstretched arms: it was that He might draw His ancient people with the one and the Gentiles with the other, and join both together in Himself. Even so, He foretold the manner of His redeeming death, "I, if I be lifted up, will draw all men unto Myself."  Again, the air is the sphere of the devil, the enemy of our race who, having fallen from heaven, endeavors with the other evil spirits who shared in his disobedience both to keep souls from the truth and to hinder the progress of those who are trying to follow it. The apostle refers to this when he says, "According to the prince of the power of the air, of the spirit that now worketh in the sons of disobedience."  But the Lord came to overthrow the devil and to purify the air and to make "a way" for us up to heaven, as the apostle says, "through the veil, that is to say, His flesh."  This had to be done through death, and by what other kind of death could it be done, save by a death in the air, that is, on the cross? Here, again, you see how right and natural it was that the Lord should suffer thus; for being thus "lifted up," He cleansed the air from all the evil influences of the enemy. "I beheld Satan as lightning falling,"  He says; and thus He re-opened the road to heaven, saying again, "Lift up your gates, O ye princes, and be ye lift up, ye everlasting doors."  For it was not the Word Himself Who needed an opening of the gates, He being Lord of all, nor was any of His works closed to their Maker. No, it was we who needed it, we whom He Himself upbore in His own body -- that body which He first offered to death on behalf of all, and then made through it a path to heaven.