Festal Orations on Pascha
Excerpt from the writings of St. Gregory the Theologian

Now then, we will examine an issue and doctrine overlooked by many but in my view very much to be examined. To whom was the blood poured out for us, and why was it poured out, that great and renowned blood of God, who is both high priest and victim? For we were held in bondage by the Evil One, sold under sin, and received pleasure in exchange for evil. But if the ransom is not given to anyone except the one holding us in bondage, I ask to whom this was paid, and for what cause? If to the Evil One, what an outrage! For the robber would receive not only a ransom from God, but God himself as a ransom, and a reward so greatly surpassing his own tyranny that for its sake he would rightly have spared us altogether. But if it was given to the Father, in the first place how? For we were not conquered by him. And secondly, on what principle would the blood of the Only begotten delight the Father, who would not receive Isaac when he was offered by his father but switched the sacrifice, giving a ram in place of the reason-endowed victim? It is clear that the Father accepts him, though he neither asked for this nor needed it, because of the divine plan, and because the human being must be sanctified by the humanity of God, that God might himself set us free and conquer the tyrant by force and lead us back to himself by the mediation of the Son, who also planned this to the honor of the Father, to whom it is manifest that he yields all things… …“Death, where is your sting? Hades, where is your victory?” By the cross you have been overthrown, by the giver of life you have been put to death. You are without breath, dead, motionless, without activity, even if you keep the form of a serpent lifted high on a pole.

†St Gregory of Nazianzus, Festal Orations, Popular Patristics Series pp. 182–183.