17 There wasn't a soul left in Ai or Bethel who wasn't out there chasing after Israel. The city was left empty and undefended as they were chasing Israel down.

Matthew Henry's Commentary on Joshua 8:17

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.