56 And if you would know what it is to 'dwell in bodily fashion,' understand what it is to speak in one that speaks, to be seen in one who is seen, to work in one who works, to be God in God, whole of whole, one of one; and thus learn what is meant by the fullness of God in bodily shape. Remember, too, that the Apostle does not keep silence on the question, whose Godhead it is, which dwells fully in Christ in bodily fashion, for he says, For the invisible things of Him since the creation of the world are clearly seen, being perceived through the things that are made, even His everlasting power and divinity. So it is His Godhead that dwells in Christ in bodily fashion, not partially but wholly, not parcelwise but in fullness; and so dwelling that the Two are one, and so one, that the One Who is God does not differ from the Other Who is God: Both so equally divine, as a perfect birth engendered perfect God. And the birth exists thus in its perfection, because the fullness of the Godhead dwells bodily in God born of God.
Source: On the Trinity (New Advent)