21 and Joshua and all Israel have seen that the ambush hath captured the city, and that the smoke of the city hath gone up, and they turn back and smite the men of Ai;

Matthew Henry's Commentary on Joshua 8:21

Commentary on Joshua 8:3-22

(Read Joshua 8:3-22)

Observe Joshua's conduct and prudence. Those that would maintain their spiritual conflicts must not love their ease. Probably he went into the valley alone, to pray to God for a blessing, and he did not seek in vain. He never drew back till the work was done. Those that have stretched out their hands against their spiritual enemies, must never draw them back.