In this passage we see 1) the virgin conception & birth of Jesus, 2) the naming of Jesus, and 3) Joseph’s response to the angel’s news about Jesus. The virgin birth is necessary, because without it, Jesus would not be fully human and fully divine. If he had two human parents, he would be merely human – just like us, another sinner in need of a savior. He would be “with us”, but he couldn’t be “God with us”. If he had no human parents, he would be divine, but totally unlike us – unable to die as our substitute; God, but not “with us”. But, because God is his Father and Mary was his mother, he was fully God and fully human in 1 person. Thus, he could truly be the savior of sinners and “God with us”.