22 Now all this was done that it might be fulfilled which the Lord spoke by the prophet, saying: 23 Behold a virgin shall be with child, and bring forth a son, and they shall call his name Emmanuel, which being interpreted is, God with us.
Jerome: Since it is introduced in the Prophet by the words, “The Lord Himself shall give you a sign” [Isa 7:14], it ought to be something new and wonderful.
Indeed the Hebrew word signifying “Virgin” (Bethula) is not used in this place, but instead the word, Halma, which except the LXX all render girl. . . . I do not think I ever met with Halma used of a married woman, but of her that is a virgin, and such that she be not merely a virgin, but in the age of youth.
Pseudo-Augustine: He, who by a touch could heal the severed limbs of others, how much more could He, in His own birth, preserve whole that which He found whole? In this parturition, soundness of the Mother’s body was rather strengthened than weakened, and her virginity rather confirmed than lost.
Theodotus: As it was God the Word who was now born in the flesh, He shewed Himself to be the Word, in that He preserved His mother’s virginity. For as our word when it is begot does not destroy the mind, so neither does God the Word in choosing His birth destroy the virginity.
Petrus Alfonsus: How can it be that this was said on account of Christ and Mary, when many centuries intervened between Ahaz and Mary? But though the Prophet was speaking to Ahaz, the prophecy was yet not spoken to him only or of his time only; for it is introduced, “Hear, O house of David” [Isa 7:13]; not, Hear, O Ahaz.
24 And Joseph rising up from sleep, did as the angel of the Lord had commanded him, and took unto him his wife.
Pseudo-Chrysostom: “Took unto him” not took home to him; for he had not sent her away; he had put her away in thought only, and now took her again in thought.
Remigius: Took her so far, as that the nuptial rites being complete, she was called his wife; but not so far as to lie with her, as it follows, “And knew her not” [v. 25].
Scripture from the Douay-Rheims Bible. Commentary from St. Thomas Aquinas, Catena Aurea, Vol. I (London: Rivington, 1842).