Jerome, on Matt 1:18

“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.”

“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 (vid. Ign. ad Eph. 19.) 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.”

Imported from an open dataset — not yet checked against the printed edition.