Charles Ellicott Commentary Joshua 7:4

"So there went up thither of the people about three thousand men: and they fled before the men of Ai." — Joshua 7:4 (ASV)

They fled before the men of Ai. —A very natural reaction from overweening confidence to utter dismay is exhibited in this incident and its effect (Joshua 7:5), the heart of the people melted and became as water. The demoralisation of Israel was a suitable penalty for their assumption, quite apart from its supernatural cause. It was absolutely necessary that the character of the conquest of Canaan should be vindicated, at whatever cost.