But what is the meaning of ‘made righteous in His Blood?” What power is there in this Blood, I demand, that believers are made righteous in it? And what of ‘reconciled through the death of His Son’? Is it really the case that, when God saw the Father was angry with us, He saw the death of His Son for us, and was appeased?…

Can we suppose that the Father would have given His own Son for us, ungrudgingly, had He not already been appeased? Is there not a contradiction here? The one passage says that the Son died for us and the Father was reconciled to us by His death. The other speaks as if the the Father loved us before, and Himself gave His Son…

Nor was the Son given up as if against His will, since it has been said of Him, ‘He loved me, and gave Himself up for me’ (Gal 2:20). Everything is the combined work of the Father, the Son, and the Spirit… in equal and harmonious activity.

The method by which man was surrendered to the devil’s power ought not to be understood in the sense that it was God’s act, or the result of God’s command: rather He merely permitted it, but He did so with justice. When God deserted the sinner, the instigator of sin rushed in… In His wrath He did not withhold His mercies… 

Therefore, God decided that, to rescue man from the devil’s power, the devil should be overcome by justice, not by power… And what is this justice by which the devil has been conquered? Surely it is the justice of Christ. And how has he been conquered? Because the devil put Christ to death, although he found in him nothing that deserved death… ‘The Prince of this world is coming, and he finds nothing (that is, no sin) in Me. But, so that all may know that I am doing My Father’s will, arise, let us go from here (Jn 14:31). And He went on from there to His passion, so that He might pay for us debtors what He Himself did not owe… In fact Christ postponed the use of power so that He might first act as was fitting. 

And for this reason it was necessary that He should be both man and God. For had He not been man, He could not have been put to death; had He not been God, man would have believed not that He did not will to exercise His power but that He had not power to achieve His will.. What could be more just than to go as far as the death of the cross for the sake of justice? What greater act of power than to rise from the dead, and to ascend to heaven with the very flesh in which He was slain? 

First justice conquered the devil, then power: justice, because He had no sin and was most unjustly put to death by the devil; power, because He lived again after death, never to die thereafter. Power would have overcome the devil, even if Christ could not have been put to death by him; and yet it showed greater power to conquer death itself by resurrection than to avoid it by continuing to live…

The devil was conquered by his own trophy of victory… By seducing the first man, he slew him: by slaying the last man, he lost the first from his snare.

St. Augustine of Hippo. “The Power and the Blood of Christ.” On the Trinity, 13 and Sermon 261.1. B#15, pp. 219-222.