"Why should the death of Christ not have come to pass? Why should that specific death have been chosen above all others, while bypassing other innumerable ways which He who is omnipotent could have employed to free us? Why does God choose that death in which neither was anything diminished or changed from His divinity and so great benefit was conferred upon men, from the humanity which He took upon Him, that a temporal death, which was not due, was rendered by the eternal Son of God, who was also the Son of man, by which He might free them from an eternal death which was due? The devil was holding fast our sins, and through them was fixing us deservedly in death. Christ discharged them, who had none of His own, and who was led by him to death undeservedly. That blood was of such price, that he who even slew Christ for a time by a death which was not due, can as his due detain no one who has put on Christ in the eternal death which was due.

"Therefore 'God commends His love towards us, in that, while we were yet sinners, Christ died for us. Much more then, being now justified in His blood, we shall be saved from wrath through Him.' Justified, he says, in His blood,-justified plainly, in that we are freed from all sin; and freed from all sin, because the Son of God, who knew no sin, was slain for us. Therefore 'we shall be saved from wrath through Him;' from the wrath of God certainly, which is nothing else but just retribution. For the wrath of God is not, as is that of man, an agitation of the mind; but it is the wrath of Him to whom Holy Scripture says in another place, 'But You, O Lord, mastering Your power, judge with calmness' (Wisdom 12:18 VUL).

"If, therefore, the just retribution of God has received such a name, what can be the right understanding also of the reconciliation of God, unless such wrath comes to an end? Neither were we enemies to God, except as sins are enemies to righteousness; which being forgiven, such enmities come to an end. Those whom He Himself justifies are reconciled to the Just One. And yet certainly He loved them even while still enemies, since 'He spared not His own Son, but delivered Him up for us all,' when we were still enemies. And therefore the apostle has rightly added: 'For if, when we were enemies, we were reconciled to God by the death of His Son,' by which that remission of sins was made, 'much more, being reconciled, we shall be saved in His life.' Saved in life, who were reconciled by death. For who can doubt that He will give His life for His friends, for whom, when enemies, He gave His death? 'And not only so,' the apostle says, 'but we also joy in God, through our Lord Jesus Christ, by whom we have now received atonement.' 'Not only,' he says, 'shall we be saved,' but 'we also rejoice;' and not in ourselves, but 'in God;' nor through ourselves, 'but through our Lord Jesus Christ, by whom we have now received atonement,' as we have argued above.

"Then the apostle adds, 'Therefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, in whom all have sinned' (Rm 5:8, 12) and so on. In this passage he disputes at some length concerning the two men; the one the first Adam, through whose sin and death we, his descendants, are bound by, as it were, hereditary evils; and the other the second Adam, who is not only man, but also God, by whose payment for us of what He owed not, we are freed from the debts both of our first father and of ourselves. Further, since on account of that one the devil held all who were begotten through his corrupted carnal desire, it is just that on account of this one he should loose all who are regenerated through His immaculate spiritual grace." 

Augustine, On the Trinity, 13.17