He said - The reading in the Hebrew text is “they said.” Joshua no doubt issued his orders through the “officers of the people” (compare Joshua 1:10).
Him that is armed - i. e. the warriors generally, not a division only. “The rereward” Joshua 6:9 was merely a detachment, and not a substantial portiere of the host; and was told off, perhaps, from the tribe of Dan (compare the marginal reference) to close the procession and guard the ark from behind. Thus the order would be
(1) the warriors,
(2) the seven priests blowing the cornets,
(3) the ark,
(4) the rear-guard.