Hilary of Poitiers

Note well the breathtaking economy by which the Son assumed flesh: Through the obedience of the one who was in the form of God [and] was emptying himself of the form of God, [he] was born as a man. In doing so, he took a new nature upon himself! This occurred not by a loss of his power and nature but by an assumption of a new condition.… Though he retained the power of his nature as God, he was in much of his earthly ministry temporarily relinquishing his exercise of the power of his nature as God as he walked as a man. The effect of this economy of order was this: The Son in his entirety, namely, as both man and God, was now, through the indulgence of the Father's will, in union with the nature of the Father. This is what occurred to God the Son: that he became a man.