12 But perhaps some may suppose that He was destitute of that glory for which He prayed, and that His looking to be glorified by a Greater is evidence of want of power. Who, indeed, would deny that the Father is the greater; the Unbegotten greater than the Begotten, the Father than the Son, the Sender than the Sent, He that wills than He that obeys? He Himself shall be His own witness:— The Father is greater than I. It is a fact which we must recognise, but we must take heed lest with unskilled thinkers the majesty of the Father should obscure the glory of the Son.
Such obscuration is forbidden by this same glory for which the Son prays; for the prayer, Father glorify Your Son, is completed by, That the Son may glorify You. Thus there is no lack of power in the Son, Who, when He has received this glory, will make His return for it in glory. But why, if He were not in want, did He make the prayer? No one makes request except for something which he needs. Or can it be that the Father too is in want? Or has He given His glory away so recklessly that He needs to have it returned Him by the Son?
No; the One has never been in want, nor the Other needed to ask, and yet Each shall give to the Other. Thus the prayer for glory to be given and to be paid back is neither a robbery of the Father nor a depreciation of the Son, but a demonstration of the power of one Godhead resident in Both. The Son prays that He may be glorified by the Father; the Father deems it no humiliation to be glorified by the Son. The exchange of glory given and received proclaims the unity of power in Father and in Son.
Source: On the Trinity (New Advent)