And thou shalt do to Ai and her king as thou didst to Jericho and her king,.... Burn the one and slay the other:

only the spoil thereof, and the cattle thereof, shall ye take for a prey unto yourselves; which they were not allowed to do at Jericho:

lay thee an ambush for the city behind it; at the west side of it: some have called in question the lawfulness of the ambush, but, as this was appointed by the Lord, there is no room for it.

Joshua was to do the same to Ai and her king as he had already done to Jericho and her king, except that in this case the conquerors were to be allowed to appropriate the booty and the cattle to themselves. In order to conquer the town, he was to lay an ambush behind it.

(Note: The much agitated question, whether it could be worthy of God to employ stratagem in war, to which different replies have been given, has been answered quite correctly by Calvin. "Surely," he says, "wars are not carried on by striking alone; but they are considered the best generals who succeed through art and counsel more than by force ... . Therefore, if war is lawful at all, it is beyond all controversy that the way is perfectly clear for the use of the customary arts of warfare, provided there is no breach of faith in the violation of treaty or truce, or in any other way.")

ארב, a collective noun, signifying the persons concealed in ambush; מארב (Joshua 8:9), the place of ambush. "Behind it," i.e., on the west of the town.

And thou shalt do to Ai and her king as thou didst unto Jericho and her king: only the spoil thereof, and the cattle thereof, shall ye take for a prey unto yourselves: lay thee an ambush for the city {a} behind it.

(a) Meaning on the west side, as in Jos 8:9.

8:2 To Ai - That is, the city and people of Ai. Unto Jericho and her king - That is, overcome and destroy them. 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.

8:1,2 When we have faithfully put away sin, that accursed thing which separates between us and God, then, and not till then, we may look to hear from God to our comfort; and God's directing us how to go on in our Christian work and warfare, is a good evidence of his being reconciled to us. God encouraged Joshua to proceed. At Ai the spoil was not to be destroyed as at Jericho, therefore there was no danger of the people's committing such a trespass. Achan, who caught at forbidden spoil, lost that, and life, and all; but the rest of the people, who kept themselves from the accursed thing, were quickly rewarded for their obedience. The way to have the comfort of what God allows us, is, to keep from what he forbids us. No man shall lose by self-denial.