Ver. 12, 13. And the children of Reuben, &c.— In conformity to their engagement, (Numbers 32:20; Numbers 21:27 and chap. Joshua 1:13.) these two tribes and a half supplied a body which passed over the Jordan, marching into the enemy's country at the head of all the people. This was evidently a chosen troop; for in the numbering, which had been made a year before, of the soldiers which each tribe could furnish, 43,730 were found in the single tribe of Reuben, 40,500 in that of Gad, and 26,350 in the half tribe of Manasseh; in all 110,580 fighting men. See Numbers 18:32. Most of them, therefore, remained on this side the Jordan, to guard the country which those tribes had conquered, and which had been given to them.
Armed— Or, Ready-girt.
Passed over—to the plains of Jericho— These 40,000 men formed the vanguard of the army, and took their march across the plains which lay betwixt Jordan and Jericho, in the place where the enemy's army should naturally have posted itself, either to dispute the passage of the Israelites through the river, or to defend the country. Thus they went on in order of battle before the ark, and, as it seems, at 2000 cubits from it.