All this took place to fulfill what the Lord had said through the prophet: "The virgin will be with child and will give birth to a son, and they will call him Immanuel--which means, 'God with us'."
When Joseph woke up, he did what the angel of the Lord had commanded him and took Mary home as his wife. But he had no union with until she gave birth to a son. And he gave him the name Jesus.
Matthew 1:22-25 (NIV)