WHY was the Lord conceived of a virgin already espoused, rather than of one as yet unpledged to a man?
For one thing, because from the genealogy of Joseph the lineage of Mary as a descendant of David, and thus of her Child, could be the more easily established.
For another, because by this betrothal Mary would be saved from being stoned by the Jews as an adulteress.
Again, because thereby Mary was given a guardian during the flight into Egypt.
To these reasons the Martyr Ignatius addeth another, namely ; that the virgin birth might take place unknown to the devil, who would naturally suppose that Mary had conceived by Joseph.
BEFORE they came together, she was found with child, of the Holy Ghost. That is, she was found so to be by Joseph, not by any one else, for he already had almost an husband's privilege to know all that concerned her. But when it is said : Before they came together : it doth not follow that they ever did come together carnally. The Scripture is to be understood merely in the sense that up to this time they had not done so.
THEN Joseph her husband, being a just man, and not willing to make her a public example, was minded to put her away privily. If any man be joined to a woman who hath lived in fornication, they in such wise become one person, that, according to the Law, they both are guilty of the crime if they both be privy to it. How then can it be that Joseph is described as a just man, at the very time he was compounding criminality in his espoused wife, to save her from the punishment demanded by the Law? This is a testimonial to Mary. For it indicateth that he knew her to be a pure virgin, and that even though he understood not the mystery of her pregnancy, yet on account of his entire trust in her, he was willing to hold his peace.
From an Anglican Breviary
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