5 But what are we to make of the words, “Whom You gave me out of the world”? For it is said of them that they were not of the world. But this they attained to by regeneration, and not by generation. And what, also, of that which follows, “Yours they were, and You gave them me”? Was there a time when they belonged to the Father, and not to His only-begotten Son; and had the Father once on a time anything apart from the Son? Surely not. Nevertheless, there was a time when God the Son had something, which that same Son as man possessed not; for He had not yet become man of an earthly mother, when He possessed all things in common with the Father.
Wherefore in saying, “Yours they were,” there is thereby no self-disruption made by God the Son, apart from whom there was nothing ever possessed by the Father; but it is His custom to attribute all the power He possesses to Him, of whom He Himself is, who has the power. For of whom He has it that He is, of Him He has it that He is able; and both together He always had, for He never had being without having ability. Accordingly, what ever the Father could [do], always side by side with Him could the Son; since He, who never had being without having ability, was never without the Father, as the Father never was without Him.
And thus, as the Father is eternally omnipotent, so is the Son co-eternally omnipotent; and if all-powerful, certainly all-possessing. For such rather, if we would speak exactly, is the word by which we translate what is called by the Greeks παντοκράτωρ which our writers would not interpret by the term omnipotent, seeing that παντοκράτωρ is all-possessing, were it not that they felt it to be equivalent in meaning. What, then, could the eternal all-possessing ever have, that the co-eternal all-possessing had not likewise?
In saying, therefore, “And You gave them me,” He intimated that it was as man He had received this power to have them; seeing that He, who was always omnipotent, was not always man. Accordingly, while He seems rather to have attributed it to the Father, that He received them from Him, since all that is, is of Him, of whom He is; yet He also gave them to Himself, that is, Christ, God with the Father, gave men to the manhood of Christ, which had not its being with the Father. Finally, He who says in this place, “Yours they were, and You gave them me,” had already said in a previous passage to the same disciples, “I have chosen you out of the world.” Here, then, let every carnal thought be crushed and annihilated.
The Son says that the men were given Him by the Father out of the world, to whom He says elsewhere, “I have chosen you out of the world.” Those whom God the Son chose along with the Father out of the world, the very same Son as man received out of the world from the Father; for the Father had not given them to the Son had He not chosen them. And in this way, as the Son did not thereby set the Father aside, when He said, “I have chosen you out of the world,” seeing that they were simultaneously chosen by the Father also: as little did He thereby exclude Himself, when He said, “Yours they were,” for they were equally also the property of the Son.
But now that same Son as man received those who belonged not to Himself, because He also as God received a servant-form which was not originally His own.
Source: Tractates on the Gospel of John (New Advent)