Joseph was of the lineage of David and had to go to Bethlehem, the city of David. ... We can see how poor Joseph must have been that he could not afford to hire some old woman or neighbor to stay with Mary and look after her while he was gone.
How unobtrusively and simply do those events take place on earth that are so heralded in heaven!
(From an advent or Christmas sermon by Martin Luther, in a book where it is not carefully sourced so I'm not sure exactly which sermon, or where to find it in his larger collected works.)
Merry and blessed Christmas to all.