Augustine of Hippo

(Tract. lxxviii. 1) Though He was only going for a time, their hearts would be troubled and afraid for what might happen before He returned; lest in the absence of the Shepherd the wolf might attack the flock: Ye have heard how I said unto you, I go away, and come again to you. In that He was man, He went: in that He was God, He stayed. Why then be troubled and afraid, when He left the eye only, not the heart? To make them understand that it was as man that He said, I go away, and come again to you; He adds, If ye loved Me ye would rejoice, because I said, I go unto My Father; for My Father is greater than I. In that the Son then is unequal with the Father, through that inequality He went to the Father, from Him to come again to judge the quick and dead: in that He is equal to the Father, He never goes from the Father, but is every where altogether with Him in that Godhead, which is not confined to place. Nay, the Son Himself, because that being equal to the Father in the form of God, He emptied Himself, not losing the form of God, but taking that of a servant, is greater even than Himself: the form of God which is not lost, is greater than the form of a servant which was put on. In this form of a servant, the Son of God is inferior not to the Father only, but to the Holy Ghost; in this the Child Christ was inferior even to His parents; to whom we read, He was subject. Let us acknowledge then the twofold substance of Christ, the divine, which is equal to the Father, and the human, which is inferior. But Christ is both together, not two, but one Christ: else the Godhead is a quaternity, not a Trinity. Wherefore He says, If ye loved Me, ye would rejoice, because I said, I go to the Father; for human nature should exult at being thus taken up by the Only Begotten Word, and made immortal in heaven; at earth being raised to heaven, and dust sitting incorruptible at the right hand of the Father. Who, that loves Christ, will not rejoice at this, seeing, as he doth, his own nature immortal in Christ, and hoping that He Himself will be so by Christ.