This is how Jesus the Messiah was born. His mother, Mary, was engaged to be married to Joseph. But before the marriage took place, while she was still a virgin, she became pregnant through the power of the Holy Spirit. Joseph, her fiance, was a good man and did not want to disgrace her publicly, so he decided to break the engagement quietly. As he considered this, an angel of the Lord appeared to him in a dream. "Joseph, son of David," the angel said, "do not be afraid to take Mary as your wife. For the child within her was conceived of the Holy Spirit. And she will have a son, and you are to name him Jesus, for he will save his people from their sins." All is occurred to fulfill the Lord's message through his prophet: "Look! The virgin will conceive a child! She will give birth to a son, and they will call him Immanuel. Which means "God is with us."" When Joseph woke up, he did as the angel of the Lord commanded him and took Mary as his wife. But he did not have sexual relations with her until her son was born. And Joseph named him Jesus.
So Mary is engaged to be married to Joseph. Can you imagine her trying to explain to Joseph how she got pregnant? He probably thought she was out of her mind! The whole story is so outrageous that there is no way that Joseph would believe it coming from Mary. He was a righteous man. He didn't want to shame Mary in public. He intended to end their engagement quietly. It would have been a very serious offense if he had exposed her as being pregnant. He wish to spare Mary that shame. Joseph had a part to play in the plan of God. God had to tell Joseph what was happening. An angel comes and tells him what Mary had probably already tried to tell him. He followed the command of God and took her for his wife. Here is this simple carpenter. He was chosen by God to be a stepfather. Not just any stepfather, but the stepfather of the Most High God incarnate. Think about what a challenging idea that had to be for Joseph. How do you properly raise the very Son of God? Praise God that Jesus had such a righteous and upright stepfather. God is amazing in the ways he uses the simple things of life to bring about his will.