He gave not up His life by compulsion, nor was He put to death by murderous violence, but of His own accord.  Hear what He says: I have power to lay down My life, and I have power to take it again: I yield it of My own choice to My enemies; for unless I chose, this could not be.  He came therefore of His own set purpose to His passion, rejoicing in His noble deed, smiling at the crown, cheered by the salvation of mankind; not ashamed of the Cross, for it was to save the world. St. Cyril of Jerusalem, Catechetical Lecture XIII

For what principle did the Blood of His Only-Begotten Son delight the Father, Who would not receive even Isaac, when he was being offered by his father, but changed the sacrifice, putting a ram in the place of the human victim? Is it not evident that the Father accepts Him, but neither asked for Him nor demanded Him; but on account of the Incarnation, and because humanity must be sanctified by the Humanity of God, that He might deliver us Himself, and overcome the tyrant, and draw us to Himself by the mediation of His Son, Who also arranged this to the honor of the Father, Whom it is manifest that He obeys in all things?  So much we have said of Christ; the greatest part of what we might say shall be reverenced with silence.  St. Gregory the Theologian, Second Oration on Pascha