Luke 2:4

And 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 of David.

Luke's design in this chapter was to show how it came about that Jesus was born in Bethlehem, despite the fact of Joseph and Mary's residence in Nazareth, thus fulfilling the prophecy of Micah 5:2. The only reason cited by Luke for this journey to Bethlehem was the decree of Caesar and the necessity for Joseph's obedience to it. However, it does not appear to be certain that Mary was required to make this journey. Clarke stated that "It was not necessary for Mary to have gone to Bethlehem";[7] that is, it was not necessarily a requirement of Caesar's decree that she should have gone. The priority of the decree as the reason for the journey is plain, for it was the only reason Luke mentioned; but there were doubtless other considerations also. Childers too believed that "Neither Roman nor Jewish law required Mary to accompany Joseph for this registration."[8] He assigned, as reasons why she did so, (1) the fact of their love for each other, (2) Mary's desire that Joseph should be with her for her delivery, and especially (3) the leading of the Holy Spirit; nor may we leave out of sight the presumption that Mary knew of Micah's prophecy and, guided by God's Spirit, moved toward fulfillment of it. Elizabeth had already identified Mary's unborn Son as the Messiah (1:43). However, her faith might not have been sufficiently strong to have caused her to go to Bethlehem without the occasion of Caesar's decree.

There is a possibility, at least, that under the circumstances they had decided to move to Bethlehem. Some elements of the sacred accounts, such as their remaining in the area after Jesus' birth, "indicate that when Joseph and Mary went to Bethlehem, they were considering it a permanent move."[9] Harmonizing with this suggestion is the fact that after going to Egypt, they intended to return to "the land of Israel"; but upon learning that another Herod was on the throne, and in obedience to God's warning in a dream, they went instead to Galilee (Matthew 2:21-23). Summers pointed out that "Bethlehem was the historical headquarters of the stonemason's guild,"[10] an association that included "tektons" of at least three classes of workers. These were carpenters, stonemasons, and certain kinds of farmers. Luke omitted a number of events related by Matthew, not only because they were already well known from the "many" sources used by all the Gospels, but because they did not fit into the particular design of his Gospel. Here, the big point is that the fulfillment of the prophecy of Christ's birth in Bethlehem was accomplished by the pagan lord of the empire, Augustus Caesar, whose census was the immediate cause of it.

Bethlehem ... means "place of bread," and it was appropriate that the Bread of Life should have been born there, and that the Son of David should have been born in the village so intimately associated with the history of David the shepherd king of Israel.

[7] Adam Clarke, Commentary on the Holy Bible (New York: Carlton and Porter, 1829), Vol. V, p. 369.

[8] Charles L. Childers, Beacon Bible Commentary (Kansas City, Missouri: Beacon Hill Press, 1964), p. 445.

[9] Ray Summers, op. cit., p. 37.

[10] Ibid.