Thou shalt do to Ai as thou didst unto Jericho That is, overcome and destroy the city and people. This was enjoined to chastise their last insolence, and the triumphs and blasphemies which doubtless their success had produced: and to revive the dread and terror which had been impressed upon the Canaanites by Jericho's ruin, and had been much abated by the late success of Ai. The spoil thereof shall ye take for a prey Neither the silver nor gold, nor any thing else, was separated to the use of the tabernacle, nor ordered to be destroyed, but the people were to enjoy it entirely themselves.
Lay thee an ambush for the city behind it Ai was not to be taken by miracle, as Jericho had been; now they must exercise their own wisdom. Having seen God work for them, whereby they might learn to depend on him, and give him the glory of all their success, they must now exert themselves, and be inured to self-denial and diligence, and to labour, toil, and hardship. And they must learn to outwit as well as to overpower their enemies. God himself commands them to take the town by stratagem; and therefore we may be sure that to do the like is lawful in other wars. But it must be well observed that no treaty was here violated, no oath or promise broken, no untruth told: to do any thing of this kind cannot be allowable or excusable in any war or case whatsoever. Nay, nothing was here concealed by the Israelites but their own counsels, which surely their enemies had no right to be intrusted with; nothing was dissembled and nothing counterfeited but a retreat, which was no necessary indication at all of their inability to maintain their attack, or of a design not to renew it. Common prudence, had they been governed by it, would have directed the men of Ai to have been upon their guard, and either to have kept within their own walls, or at least not to have ventured forward rashly in pursuit of an army which they saw to be very superior to them in number.