IV. The Incarnation deceived the Devil and caused him to break the bond under which he held men
When, therefore, the merciful and almighty Saviour so arranged the commencement of His human course as to hide the power of His Godhead which was inseparable from His manhood under the veil of our weakness, the crafty foe was taken off his guard and he thought that the nativity of the Child, Who was born for the salvation of mankind, was as much subject to himself as all others are at their birth. For he saw Him crying and weeping, he saw Him wrapped in swaddling clothes, subjected to circumcision, offering the sacrifice which the law required.
And then he perceived in Him the usual growth of boyhood, and could have had no doubt of His reaching man's estate by natural steps. Meanwhile, he inflicted insults, multiplied injuries, made use of curses, affronts, blasphemies, abuse, in a word, poured upon Him all the force of his fury and exhausted all the varieties of trial: and knowing how he had poisoned man's nature, had no conception that He had no share in the first transgression Whose mortality he had ascertained by so many proofs.
The unscrupulous thief and greedy robber persisted in assaulting Him Who had nothing of His own, and in carrying out the general sentence on original sin, went beyond the bond on which he rested, and required the punishment of iniquity from Him in Whom he found no fault. And thus the malevolent terms of the deadly compact are annulled, and through the injustice of an overcharge the whole debt is cancelled. The strong one is bound by his own chains, and every device of the evil one recoils on his own head.
When the prince of the world is bound, all that he held in captivity is released. Our nature cleansed from its old contagion regains its honourable estate, death is destroyed by death, nativity is restored by nativity: since at one and the same time redemption does away with slavery, regeneration changes our origin, and faith justifies the sinner.
Source: Sermons (New Advent)