Luke 2: 1-5
In those days Caesar Augustus issued a decree that a census should be taken of the entire Roman world. This was the first census that took place while Quirinius was governor of Syria. And everyone went to his own town to register.
So Joseph also went up from the town of Nazareth in Galilee to Judea to Bethlehem, the town of David, because he belonged to the house and line of David. He went there to register with Mary, who was pledged to marry him and was expecting a child.