Let’s review: A man, Joseph, whose life is turned upside down. A vulnerable girl. The time cues in the story; the “now” of the story. The holy spirit. Family and relationships — particularly healed relationships.
This is a lot for just a few verses!
Perhaps what strikes me today, right now, is the “dream-ness” of this. We don’t know at first Joseph has fallen asleep — was he turning over his “Mary problem” as he was lying in bed, the way one does, an endless night of worry, the same thoughts churning in your mind, over and over? We don’t know. We are told:
“But just when he had resolved to do this, an angel of the Lord appeared to him in a dream…”
And then later “when Joseph awoke from sleep”…
Now there is another biblical Joseph, who also dreamed, back in Genesis. I seem to keep connecting this nativity story to Genesis. Joseph’s dream made his brothers so angry, they sold him to folk who took him to Egypt. And then his dreams caused him him to rise in influence with Pharaoh. Joseph was a famous dreamer, this is the merest bare bones of the hint of the story (Genesis 37 and others). But what that Joseph did most of all was help Israel survive, because what man intended for evil, God turned to good (Genesis 45:4-5). The line of David does not spring from Joseph, but without Joseph there would have been no house of David.
Likewise, without this Joseph, Mary’s husband, son of David, there very likely would not have been survival for this child. This Joseph protected the son of God, gave him a name, gave him a trade and a family. Jesus will be the start of a new relationship between God and man, a re-genesis perhaps. So it seems appropriate for there to be another Joseph critical in ensuring the survival of this new start.