Luke 2:4-6

And Joseph also went up from Galilee, out of the city of Nazareth, into Judæa, to the city of David, which is called Bethlehem, because he was of the house and family of David; to enrol himself with Mary, who was betrothed to him, being great with child. And it came to pass, while they were there, the days were fulfilled that she should be delivered.