[or Lk 2:41-51]
Son of David: In the Gospel, the only one called by the title “son of David” other than Jesus is Joseph. “Son of David” is a messianic title, based on the promises of God through Nathan the prophet: God would raise up a son after David and establish the throne of his kingdom forever; God would be a father to this king and the king would be God’s son (2 Sm 7:8-17). Sonship here has a sense of adoption.
In Matthew’s annunciation, the message about the conception of the Savior is addressed to Joseph who is of the house of David. The Child has been begotten in the womb of a virgin through God’s Holy Spirit. He then is the “Son of the Most High.” He becomes the Messiah, the “Son of David” through the acknowledgment of Joseph. It is Joseph who provides for him the royal Davidic line. The angel addresses Joseph as “son of David” to emphasize his lineage that he now passes to the Son of Mary.
The angel tells Joseph to name the child Jesus. By this action, Joseph acknowledges him as his own. The Jewish law prefers to base paternity of a child on the man’s acknowledgment: “If a man says, ‘This is my son,’ he is to be believed.” By exercising the father’s right to name the child, Joseph acknowledges Jesus and thus becomes the legal father of Jesus. Legal paternity among Semites is real paternity. Joseph is not just a “foster father” of Jesus in the sense that he adopts him as his own. He is the “legal father” inasmuch as he acknowledges Jesus as his legitimate son.