With Mary his espoused wife - There was no necessity for Mary to have gone to Bethlehem, as Joseph's presence could have answered the end proposed in the census as well without Mary as with her; but God so ordered it, that the prophecy of Micah should be thus fulfilled, and that Jesus should be born in the city of David; Micah 5:2.

To be taxed with Mary his espoused wife,.... Whom also he had married, though he had not known her in a carnal way; she came along with him to be taxed and enrolled also, because she was of the same family of David, and belonged to the same city:
being great with child; very near her time, and yet, though in such circumstances, was obliged by this edict, to come to Bethlehem; and the providence in it was, that she might give birth there, and so the prophecy in Micah 5:2 have its accomplishment: this was an instance, and an example, of obedience to civil magistrates.

espoused wife--now, without doubt, taken home to him, as related in Matthew 1:18; Matthew 25:6.

To enrol himself with Mary. Women had to be enrolled also and were subject to the poll tax. Mary was of the line of David, and hence would also have to go to Bethlehem.