Luke 2:1, 3-7

And it came to pass in those days that a decree went out from Caesar Augustus that all the world should be registered.

So all went to be registered, everyone to his own city. Joseph also went up from Galilee, out of the city of Nazareth, into Judea, to the city of David, which is called Bethlehem, because he was of the house and lineage of David, to be registered with Mary, his betrothed wife, who was with child. So it was, that while they were there, the days were completed for her to be delivered. And she brought forth her firstborn Son, and wrapped Him in swaddling cloths, and laid Him in a manger, because there was no room for them in the inn.