And pitched in Aroer - This was beyond Jordan, on the river Arnon, in the tribe of Gad: hence it appears, says Calmet, that they began their census with the most eastern parts of the country beyond Jordan.

And they passed over Jordan,.... To take the number of the tribes of Reuben and Gad and the half tribe of Manasseh first:

and pitched in Aroer; for it seems that Joab and the captains had the army with them, and the several captains under their command, partly to assist in numbering the people, and partly to keep them in awe, lest they should oppose them, not knowing what was the design of all this Aroer was a city given to the tribe of Gad, and rebuilt by them, Num 32:34,

on the right side of the city; that is, of Aroer, the south side of it, as the Targum, did Joab and his army pitch:

that lieth in the midst of the river of Gad; which was the river Arnon, so called now from the tribe of Gad, which possessed it, and so the Targum, in the midst of the river of the tribe of Gad; for in the midst of the river Arnon Aroer lay, see Jos 13:9,

and toward Jazer; another city given to the Gadites, Num 32:3; and, according to Bunting (u), was sixteen miles from Aroer.

(u) Travels, &c. p. 147.

they passed over Jordan--This census was taken first in the eastern parts of the Hebrew kingdom; and it would seem that Joab was accompanied by a military force, either to aid in this troublesome work, or to overawe the people who might display reluctance or opposition.

the river of Gad--"Wady" would be a better term. It extends over a course estimated at about sixty miles, which, though in summer almost constantly dry, exhibits very evident traces of being swept over by an impetuous torrent in winter (see Deu 2:36).