Hilary of Poitiers

(de Trin. c. 16.) Or, His descending from heaven is the source of His origin as conceived by the Spirit: Mary gave not His body its origin, though the natural qualities of her sex contributed its birth and increase. That He is the Son of man is from the birth of the flesh which was conceived in the Virgin. That He is in heaven is from the power of His everlasting nature, which did not contract the power of the Word of God, which is infinite, within the sphere of a finite body. Our Lord remaining in the form of a servant, far from the whole circle, inner and outer, of heaven and the world, yet as Lord of heaven and the world, was not absent therefrom. So then He came down from heaven because He was the Son of man; and He was in heaven, because the Word, which was made flesh, had not ceased to be the Word.