The angel went to her and said, "Greetings, you who are highly favored! The Lord is with you. ...For nothing is impossible with God."Sometimes I find it encouraging to dwell on a verse and really think about the actual words used. Sometimes it can be interesting and informative to think of other ways the sentence could be formulated. Here the question came to my mind why doesn't this sentence read "For God nothing is impossible." Certainly that is true. God has no limitations and as Creator of everything he could make anything happen. Perhaps there is more here than just that fact. Yes nothing is impossible "for God", but also, as it is written here, nothing is impossible "with God". "With God" includes us. God will include us in the unbelievable things he will do. We also know from the Word that "God is with us."
All this took place to fulfill what the Lord had said through the prophet: "The virgin will conceive and give birth to a son, and they will call him Immanuel" (which means "God with us"). (Matthew 1:22-23)