41 So God is glorified in the Son of Man, Who is also Son of God. Let us see, then, what is this third clause which is added, If God is glorified in Him, God has also glorified Him in Himself. What, pray, is this secret mystery? God, in the glorified Son of Man, glorifies a glorified God in Himself! The glory of God is in the Son of Man, and the glory of God is in the glory of the Son of Man. God glorifies in Himself, but man is not glorified through himself.
Again the God Who is glorified in the man, though He receives the glory, yet is Himself none other than God. But since in the glorifying of the Son of Man, the God, Who glorifies, glorifies God in Himself, I recognise that the glory of Christ's nature is taken into the glory of that nature which glorifies His nature. God does not glorify Himself; but He glorifies in Himself God glorified in man. And this “glorifies in Himself,” though it is not a glorifying of Himself, yet means that He took the nature, which He glorified, into the glory of His own nature since the God, Who glorifies the God glorified in man, glorifies Him in Himself, He proves that the God Whom He glorifies is in Himself, for He glorifies Him in Himself.
Come, heretic, whoever you be, produce the inextricable objections of your tortuous doctrine; though they bind themselves in their own tangles, yet, marshal them as you will, we shall not be in danger of sticking in their snares. The Son of Man is glorified; God is glorified in Him; God glorifies in Himself Him, Who is glorified in the man. It is not the same that the Son of Man is glorified, as that God is glorified in the Son of Man, or that God glorifies in Himself Him, Who is glorified in the man.
Express in the terms of your unholy belief, what you mean by God being glorified in the Son of Man. It must certainly be either Christ Who is glorified in the flesh, or the Father Who is glorified in Christ. If it is Christ, Christ is manifestly God, Who is glorified in the flesh. If it is the Father, we are face to face with the mystery of the unity, since the Father is glorified in the Son. Thus, if you allow it to be Christ, despite yourself you confess Him God; if you understand it of God the Father, you cannot deny the nature of God the Father in Christ.
Let this be enough concerning the glorified Son of Man and God glorified in Him. But when we consider that God glorifies in Himself God, Who is glorified in the Son of Man, by what loophole, pray, can your profane doctrine escape from the confession that Christ is very God according to the verity of His nature? God glorifies in Himself Christ, Who was born a man; is Christ then outside Him, when He glorifies Him in Himself? He restores to Christ in Himself the glory which He had with Himself, and now that the servant's form, which He assumed, is in turn assumed into the form of God, God Who is glorified in man is glorified in Himself; He was in God's self before the dispensation, by which He emptied Himself, and now He is united with God's self, both in the form of the servant, and in the nature belonging to His birth.
For His birth did not make Him God of a new and foreign nature, but by generation He was made natural Son of a natural Father. After His human birth, when He is glorified in His manhood, He shines again with the glory of His own nature; the Father glorifies Him in Himself, when He is assumed into the glory of His Father's nature, of which He had emptied Himself in the dispensation.
Source: On the Trinity (New Advent)