To be taxed with Mary his espoused wife, being great with child.
To be taxed with Mary his espoused wife - `betrothed' "wife." She had sometime before this been taken home by Joseph (see the notes at Matthew 1:18-24); but she is so called here, perhaps, for the reason mentioned home by Joseph (see the notes at Matthew 1:18-24); but she is so called here, perhaps, for the reason mentioned in Matthew 1:25.
Being great with child. Not only does Joseph, as being of the royal line, go to Bethlehem (1 Samuel 16:1), but Mary too; not from choice, surely, in her tender condition. It is possible that in this they simply followed the Roman method, of the wife accompanying the husband; but the more likely reason would seem to be that she herself was of the family of David.