18 Now the generation of Christ was in this wise. When as his mother Mary was espoused to Joseph, before they came together, she was found with child, of the Holy Ghost.
Jerome: But why is He conceived not of a Virgin merely, but of a Virgin espoused? First, that by the descent of Joseph, Mary’s family might be made known; secondly, that she might not be stoned by the Jews as an adulteress; thirdly, that in her flight into Egypt she might have the comfort of a husband.
The Martyr Ignatius adds yet a fourth reason, namely, that His birth might be hid from the Devil, looking for Him to be born of a wife and not of a virgin.
Origen: She was indeed espoused to Joseph, but not united in wedlock.
Cyril: The Word was born of the very substance of God Himself, and without beginning of time always coexisted with the Father. But in these last times when He was made flesh, that is united to flesh, having a rational soul, He is said to be born of a woman after the flesh. . . . The Word of God was born of the substance of His Father; but because He took on Him flesh, making it His own, it is necessary to confess that He was born of a woman according to the flesh. Where seeing He is truly God, how shall any one doubt to call the Holy Virgin the Mother of God?
Pseudo-Chrysostom: Mary was therefore betrothed to a carpenter, because Christ the Spouse of the Church was to work the salvation of all men through the wood of the Cross.
Chrysostom: What follows, “Before they came together,” does not mean before she was brought to the bridegroom’s house, for she was already within. For it was a frequent custom among the ancients to have their betrothed wives home to their house before marriage.
Pseudo-Chrysostom: Joseph was absent when the things were done which Luke writes. For it is not easy to suppose that the Angel came to Mary and said those words, and Mary made her answer when Joseph was present. And even if we suppose thus much to have been possible, yet it could not be that she should have gone into the hill country, and abode there three months when Joseph was present, because he must needs have enquired the causes of her departure and long stay. And so when after so many months he returned from abroad, he found her manifestly with child.
Jerome: “Before,” though it often implies something to follow, yet often is said of things that follow only in thought; and it is not necessary that the things so thought of should take place, for that something else has happened to prevent them from taking place. . . . Therefore it by no means follows that they did come together afterwards.
Remigius: The word “come together” may not mean carnal knowledge, but may refer to the time of the nuptials, when she who was betrothed begins to be wife. Thus, “before they came together,” may mean before they solemnly celebrated the nuptial rites.
Scripture from the Douay-Rheims Bible. Commentary from St. Thomas Aquinas, Catena Aurea, Vol. I (London: Rivington, 1842).