The angel tells Joseph that his beloved Mary is pregnant not by another man as he has supposed, but by the Holy Spirit of God (Matthew 1:20).  Matthew lines their situation up with Isaiah’s prophecy, “The virigin will conceive and give birth to a son,” (1:23/Isaiah 7:14).  Joseph has two things to do:  accept Mary and her pregnancy and keep her a virign until after the birth of Jesus. The first is explicit in the text while the second is implicit.  After all, “The virgin . . . will give birth to a son.”  It’s the virigin birth --- not just the virigin conception. 

I find all of this utterly remarkable.  Mary was impregnanted before she and Joseph were to come together as husband and wife in sexual union --- I get that.  Joseph’s plan to divorce her reinforces the fact to the world around them that they haven’t been together and the child isn’t his (even though he was going to divorce her "quietly," people would still find out).   I understand that as well.  But then that God has them marry and then refrain from sexual relations so that the virigin will give birth to a son, well . . . that’s an unbelievably risky stategy, don't you think?

Some day in the future, when the great deeds of faith are rehearsed and celebrated, they’ll rightly speak of David slaying Goliath, and Paul traveling all over the world to share Christ with others.  They’ll be talk of the anointing of Jesus by a different Mary, of Noah's boat-building, Abraham and Sarah heading off to who knows where, and Daniel suriviving the lions.  And some point, someone will say something about the two young newlyweds who for sake of God postponed a marital privilege so they could partner with their Father in His plans for the world.