53 So the Only-begotten God, just before He finished His work in the flesh, and completed the mystery of taking the servant's form, in order to establish our faith, thus speaks, You heard how I said unto you, I go away, and I came unto you. If you loved Me, you would rejoice, because I go unto the Father; for the Father is greater than I. He has already, in an earlier part of this very discourse unfolded in all its aspects the teaching of His divine nature: can we, then, on the strength of this confession deprive the Son of that equality, which His true birth has perfected in Him?
Or is it an indignity to the Only-begotten God, that the Unbegotten God is His Father, seeing that His Only-begotten birth from the Unbegotten gives Him the Only-begotten nature? He is not the source of His own being, nor did He, being Himself non-existent, bring to pass His own birth out of nothing; but, existing as a living nature and from a living nature, He possesses the power of that nature, and declares the authority of that nature, by bearing witness to His honour, and in His honour to the grace belonging to the birth He received. He pays to the Father the tribute of obedience to the will of Him Who sent Him, but the obedience of humility does not dissolve the unity of His nature: He becomes obedient unto death, but, after death, He is above every name.
Source: On the Trinity (New Advent)