Learning the way of peace in the Eucharist

From a lecture on the Eucharist entitled "Training in the peace of Messiah" by Dr. Tommy Givens 

"If man is in the likeness of God, and rules the whole earth, and has been granted authority over everything on earth from God, who is his buyer, tell me? Who is his seller? To God alone belongs this power; or rather, not even to God himself. For his gracious gifts, it says, are irrevocable (Romans 11:29). God would not therefore reduce the human race to slavery, since he himself, when we had been enslaved to sin, spontaneously recalled us to freedom. But if God does not enslave what is free, who is he that sets his own power above God’s? (Gregory of Nyssa, Fourth Homily on Ecclesiastes)