And Moses said unto them,.... Being better disposed towards them, and more satisfied with the reasonableness of their request, it being explained unto him:

if ye will do this thing; which they had promised:

if ye will go armed before the Lord to war; they had said they would go ready armed before the children of Israel, but Moses expresses it "before the Lord"; which is more agreeable to their encampment and order in marching, for not the standard of Reuben but that of Judah went foremost, yet the standard of Reuben marched directly before the sanctuary bore by the Kohathites, Num 10:18, and so might be properly said to go before the Lord, who dwelt there.

and our little ones shall dwell in the fenced cities because of the inhabitants of the land--There was good policy in leaving a sufficient force to protect the conquered region lest the enemy should attempt reprisals; and as only forty thousand of the Reubenites and the Gadites, and a half of Manasseh, passed over the Jordan (Jos 4:13), there were left for the security of the new possessions 70,580 men, besides women and children under twenty years (compare Num 26:7, Num 26:18, Num 26:34).

We ourselves will go ready armed--that is, all of us in a collective body, or as many as may be deemed necessary, while the rest of our number shall remain at home to provide for the sustenance and secure the protection of our families and flocks. (See on Jos 4:12).