22 And furthermore, let His own Divine words bear witness to Himself. He says, They that are of My sheep hear My voice, and I know them, and they follow Me; and I give unto them eternal life, and they shall never perish, neither shall any man pluck them of My hand. That which My Father has given Me is greater than all, and no man shall be able to pluck them out of My Father's hand. I and the Father are one. What lethargy can blunt so utterly the edge of our understanding as to render so precise a statement for one moment obscure to us?
What proud sophistry can play such pranks with human docility as to persuade those, who have learned from these words the knowledge of what God is that they must not recognise God in Him Whose Godhead was here revealed to them? Heresy ought either to bring forward other Gospels in support of its doctrine; or else, if our existing Gospels are the only documents which teach of God, why do they not believe the lessons taught? If they are the only source of knowledge, why not draw faith, as well as knowledge, from them?
Yet now we find that their faith is held in defiance of their knowledge; and hence it is a faith rooted not in knowledge, but in sin; a faith of bold irreverence, instead of reverent humility, towards the truth confessedly known. God the Only-begotten, as we have seen, fully assured of His own nature, reveals with the utmost precision of language the mystery of His birth. He reveals it, ineffable though it is, in such wise that we can believe and confess it; that we can understand that He was born and believe that He has the nature of God and is One with the Father, and One with Him in such a sense that God is not alone nor Son another name for Father, but that in very truth He is the Son.
For, firstly, He assures us of the powers of His Divine nature, saying of His sheep, and no man shall pluck them out of My hand. It is the utterance of conscious power, this confession of free and irresistible energy, that will allow no man to pluck His sheep from His hand. But more than this; not only has He the nature of God, but He would have us know that nature is His by birth from God, and hence He adds, That which the Father has given Me is greater than all.
He makes no secret of His birth from the Father, for what He received from the Father He says is greater than all. And He Who received it, received it at His birth, not after His birth, and yet it came to Him from Another, for He received it. But He, Who received this gift from Another, forbids us to suppose that He Himself is different in kind from That Other, and does not eternally subsist with the same nature as that of Him Who gave the gift, by saying, No man shall be able to pluck them out of My Father's hand.
None can pluck them out of His hand, for He has received from His Father that which is greater than all things. What, then, means this contradictory assertion that none can pluck them from His Father's hand? It is the Son's hand which received them from the Father, the Father's hand which gave them to the Son: in what sense is it said that what cannot be plucked from the Son's hand cannot be plucked from the Father's hand? Hear, if you wish to know:— I and the Father are one.
The Son's hand is the Father's hand. For the Divine nature does not deteriorate or cease to be the same in passing through birth: nor yet is this sameness a bar to our faith in the birth, for in that birth no alien element was admitted into His nature. And here He speaks of the Son's hand, which is the hand of the Father, that by a bodily similitude you may learn the power of the one Divine nature which is in Both; for the nature and the power of the Father is in the Son. And lastly, that in this mysterious truth of the birth you may discern the true and indistinguishable unity of the nature of God, the words were spoken, I and the Father are One.
They were spoken that in this unity we might see neither difference nor solitude; for They are Two, and yet no second nature came into being through that true birth and generation.
Source: On the Trinity (New Advent)