“Behold, the virgin will be with child and will give birth to a son, and they will call Him Immanuel” (which means, “God with us”).
23. His name Immanuel The phrase, God is with us, is no doubt frequently employed in Scripture to denote, that he is present with us by his assistance and grace, and displays the power of his hand in our defense. But here we are instructed as to the manner in which God communicates with men.
The mystery of Christ's incarnation is to be adored, not pried into. If we know not the way of the Spirit in the formation of common persons, nor how the bones are formed in the womb of any one that is with child (Ecc 11:5), much less do we know how the blessed Jesus was formed in the womb of the blessed virgin.
Commenting on Matthew 1:18-25
Behold, a virgin shall be with child,.... These words are rightly applied to the virgin Mary and her son Jesus, for of no other can they be understood; not of Ahaz's wife and his son Hezekiah, who was already born, and must be eleven or twelve years of age when these words were spoken; nor of any other son of Ahaz by her or any...