Would Mary Have Sinned by Saying No to God?

Theoretically, a no from Mary at the Annunciation could have been sinful, though it’s also possible that she could have said no without sinning.

More to the point, in actuality, we know that Mary didn’t sin. Still, it’s theoretically possible Mary could have said no at the Annunciation, and Jimmy Akin addresses this issue in a radio response, as do I in an online answer regarding whether Mary was forced to be the Mother of God.