What does Matthew 1:20 mean?
From Joseph's initial perspective, his betrothed, Mary, has betrayed him. She has been found to be pregnant, and he is not the father. To assume she was unfaithful is exactly how anyone would react in that situation. If that is the case, Mary has violated the legally-binding agreement to marry Joseph. Yet Joseph shows an exceptionally decent response to what looks like obvious infidelity.Instead of flying into a rage or exposing her to the community, Joseph demonstrates that he is "a just man" (Matthew 1:19) by planning to divorce her a quietly as possible. He has no interest in bringing greater shame on her or her family.
Before he takes that action, however, an angel of the Lord shows up in one of Joseph's dreams. This is not the last time Joseph will have the experience of being directed by God through an angel messenger in a dream. This angel has a very specific message for Joseph: Don't divorce Mary!
More specifically, the angel calls Joseph a son of David, which backs up Matthew's message that Jesus, also, is a direct descendant of David. The angel tells Joseph not to be afraid to take Mary as his wife, despite his legitimate concerns about her pregnancy, and what it means about her character and trustworthiness. The angel reveals to Joseph what is really going on. She is not pregnant as a result of having sex with another man. The baby conceived in her is miraculously given from the Holy Spirit.
Matthew 1:18–25 tells the story of the birth of Christ from the perspective of Joseph. This man is betrothed to be married to Mary, but finds out she is pregnant. He does not realize, yet, that this child is Christ, and that she is pregnant by a miracle of the Holy Spirit. God interrupts Joseph's honorable plans to divorce Mary, and tells him through an angel in a dream not to fear taking her as a wife and that the child is from God. Jesus will fulfill Isaiah's prophecy that Immanuel, ''God with us,'' will be born to a virgin. Joseph obeys, demonstrating his faith in God.
The apostle Matthew begins his telling of Jesus' life with a genealogy. This is meant to show that Jesus is directly descended from both Abraham and King David, making Him a legal heir to the throne of Israel. He then tells the story of Jesus' birth from the perspective of Joseph, Mary's husband. Joseph had planned to divorce the woman he was betrothed to marry, once he found out she was carrying a child that wasn't his. God interrupts this plan. An angel tells Joseph in a dream that the child is from the Holy Spirit and commands Joseph to name Him Jesus, since He will save His people from their sins. Joseph obeys.
