What does Luke 1:31 mean?

The angel Gabriel is delivering his second announcement of a miraculous birth in this chapter (Luke 1:11–13; 19). The first was to tell an aging priest and his wife (Luke 1:5–7) that they would finally have a son. Now, the angel has come to a virgin—a woman who has never been intimate with a man (Luke 1:34)—to tell her she, too, will conceive. Mary's willingness to obey God does not remove all possible questions, of course. She trusts that the angel's words are true, but will ask how—meaning, in what way—God will accomplish this task.

The answer is that her conception will be from the Holy Spirit, rather than from intercourse (Luke 1:35). The result of that conception will be Jesus, the Messiah and Son of God (Luke 1:32–33).

Such news corresponds to Old Testament prophecies. Mary has never had intercourse, and yet she will bear a son (Isaiah 7:14). That child will be born to a woman in the family of king David (Luke 3:23–38), whose husband will also be in that line (Matthew 1:1–17), as predicted (2 Samuel 7:12–16; Isaiah 9:6–7). This role is a profound honor (Luke 1:28), though it mostly involves Mary's faithful submission, rather than any extraordinary work of her own (Luke 1:38).