The rereward being opposed to the armed men, may seem to note the unarmed people, who were desirous to be spectators of this wonderful work. The priests; which is rightly supplied here from Joshua 6:4.
Related Commentaries of Joshua 6:9
Joshua 6:9
9 And the armed men went before the priests that blew with the trumpets, and the rerewardb came after the ark, the priests going on, and blowing with the trumpets.