Joshua 8:10

And Joshua rose up early in the morning, and numbered the people, and went up, he and the elders of Israel, before the people to Ai.

Joshua ... numbered the people - i:e., the detachment of liers-in-wait; he did this, to be furnished with clear evidence afterward, that the work had been done without any loss of men, whereby the people's confidence in God would be strengthened, and encouragement given them to prosecute the war of invasion with vigour.

He and the elders of Israel - the chief magistrates and rulers, whose presence and official authority were necessary to ensure that the cattle and spoil of the city might be equally divided between the combatants and the rest of the people (Numbers 31:27) - a military rule in Israel that would have been very liable to be infringed if an excited soldiery, eager for booty, had been left to their own will.