John 14:28

28.If you loved me you would rejoice. The disciples unquestionably loved Christ, but not as they ought to have done; for some carnal affection was mixed with their love, so that they could not endure to be separated from him; but if they had loved him spiritually, there was nothing which they would have had more deeply at heart, than his return to the Father.

For the Father is greater than I. This passage has been tortured in various ways. The Aryans, in order to prove that Christ is some sort of inferior God, argued that he is less than the Father The orthodox Fathers, to remove all ground for such a calumny, said that this must have referred to his human nature; but as the Aryans wickedly abused this testimony, so the reply given by the Fathers to their objection was neither correct nor appropriate; for Christ does not now speak either of his human nature, or of his eternal Divinity, but, accommodating himself to our weakness, places himself between God and us; and, indeed, as it has not been granted to us to reach the height of God, Christ descended to us, that he might raise us to it. You ought to have rejoiced, he says, because I return to the Father; for this is the ultimate object at which you ought to aim. By these words he does not show in what respect he differs in himself from the Father, but why he descended to us; and that was that he might unite us to God; for until we have reached that point, we are, as it were, in the middle of the course. We too imagine to ourselves but a half-Christ, and a mutilated Christ, if he do not lead us to God.

There is a similar passage in the writings of Paul, where he says that Christ

will deliver up the Kingdom to God his Father, that God may be all in all,
(1 Corinthians 15:24.)

Christ certainly reigns, not only in human nature, but as he is God manifested in the flesh. In what manner, therefore, will he lay aside the kingdom? It is, because the Divinity which is now beheld in Christ’s face alone, will then be openly visible in him. The only point of difference is, that Paul there describes the highest perfection of the Divine brightness, the rays of which began to shine from the time when Christ ascended to heaven. To make the matter more clear, we must use still greater plainness of speech. Christ does not here make a comparison between the Divinity of the Father and his own, nor between his own human nature and the Divine essence of the Father, but rather between his present state and the heavenly glory, to which he would soon afterwards be received; as if he had said, “You wish to detain me in the world, but it is better that I should ascend to heaven.” Let us therefore learn to behold Christ humbled in the flesh, so that he may conduct us to the fountain of a blessed immortality; for he was not appointed to be our guide, merely to raise us to the sphere of the moon or of the sun, but to make us one with God the Father.