Pope St. Leo the Great ca. 400-461
… [W]e bade the simple and unthinking hearer not take the words My God, etc.,
in a sense as if, when Jesus was fixed upon the wood of the cross, the Omnipotence of the Father’s Deity had gone away from Him; seeing that God’s and Man’s Nature were so completely joined in Him that the union could not be destroyed by punishment nor by death. For while each substance retained its own properties, God neither held aloof from the suffering of His body nor was made passible by the flesh, because the Godhead which was in the Sufferer did not actually suffer. And hence, in accordance with the Nature of the Word made Man, He Who was made in the midst of all is the same as He through Whom all things were made. He Who is arrested by the hands of wicked men is the same as He Who is bound by no limits. He Who is pierced with nails is the same as He Whom no wound can affect. Finally, He Who underwent death is the same as He Who never ceased to be eternal, so that both facts are established by indubitable signs, namely, the truth of the humiliation in Christ and the truth of the majesty; because Divine power joined itself to human frailty to this end, that God, while making what was ours His, might at the same time make what was His ours. The Son, therefore, was not separated from the Father, nor the Father from the Son; and the unchangeable Godhead and the inseparable Trinity did not admit of any division. For although the task of undergoing Incarnation belonged peculiarly to the Only-begotten Son of God, yet the Father was not separated from the Son any more than the flesh was separated from the Word. (Sermon 68.1)
