“He who eats My flesh and drinks My blood abides in Me, and I in him. 57 As the living Father sent Me, and I live because of the Father, so he who eats Me, he also will live because of Me. 58 This is the bread which came down out of heaven; not as the fathers ate and died; he who eats this bread will live forever.” John 6:56-58 NASB
“I live because of the Father”, the Lord said. Here we see that the Son is caused, not having life without cause or origin, but having His life, His being and existence, from the Father. And this text refutes the one who seeks to deprive these words of their force by appealing to the humanity of Christ, as though He had only said that His flesh lived because of the Father, for He says “As the living Father sent Me, and I live because of the Father.” Hear, then that He Who lives because of the Father is He Who was sent by the Father; not the flesh, which, when He had came, the Word took on Himself, but the Word Himself Who was sent, lives because of the Father. And this is confirmed again, by the next verse, when He declares “This is the bread which came down out of heaven”; for it was not His flesh that came down out of heaven, but the Word Himself, the Son of God.
It is shown, then, that the Son, as Son, lives because of the Father; and this is important to note, as it refutes the heresy of the Modalists, Who say that the Son is Himself the Supreme Being, together with the Father. For the Father is uncaused, having no one greater than Himself, as the Lord said “My Father, who has given them to Me, is greater than all” John 10:29 NASB. And so it is evident that the Supreme Being, Who is alone the supreme uncaused Cause of all else that exists, is the Father alone, the Son not being the Supreme Being Himself, but another distinct individual being, Who lives because of the Father: and so it is shown that the one God, the Supreme Being, is Father of a Son, His only-begotten Son our Lord.