The signification of His opening words cannot, I think, be doubted, Now is the Son of Man glorified; that is, all the glory which He obtains is not for the Word but for His flesh: not for the birth of His Godhead, but for the dispensation of His manhood born into the world. What then, may I ask, is the meaning of what follows, And God is glorified in Him? God is glorified in Him, in the Son of Man, that is: tell me, then, is the Son of Man the same as the Son of God? And since the Son of Man is not one and the Son of God another, but He Who is Son of God is Himself also Son of Man, Who, pray, is the God Who is glorified in this 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 hath also glorified Him in Himself. 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. God being glorified in the Son of Man 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. 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? The Father glorifies Him, not with a glory from without, but in Himself. By taking Him back into that glory, which belongs to Himself, and which He had with Him before, the Father glorifies Him with Himself and in Himself.
Source: ON THE TRINITY 9.40-42