Luke 2:3

And all went to be taxed— When the census was made in any country under the dominion of the Romans, the inhabitants were obligedto attend in the cities to which they belonged. See Livy, lib. 42. 100: 10. The reason was, that without a precaution of this kind, the census would have been excessively tedious, and people who were abroad might have been omitted, or set down among the inhabitants of other cities, where they would not have been found afterwards; or they might have been enrolled twice, which would have bred confusion in the registers. Herod, who, it is probable, executed the census in his own dominions by the appointment of Augustus, seems to have made a small alteration in the mode of it; for instead of ordering the people to appear, as usual, in the cities where they resided, or to whose jurisdictions the places of their abode belonged, he ordered them to appear according to their families; perhaps, because it was the ordinary way of classing the Jewish people, or because he desired to know the number and strength of the dependants of the great families in his dominions. But on whatever account the alteration was made, it appears to have been owing to a providential interposition; for otherwise Christ might not have been born at Bethlehem, his mother and reputed father having long resided at Nazareth, and having no other cause for changing their situation when Mary was so near her time, unless on some such necessity. We may just observe further, that this obedience of the Jews to the decree of Caesar, is a plain proof that they were now dependant on the Romans, and that the sceptre was departing from Judah. See Lightfoot's Harmony, and compare Genesis 49:10 and Numbers 24.