Joshua 8:19-23

They entered and set the city on fire That is, some part of it, sufficient to raise a smoke, and give notice to their brethren of their success. But certainly not all of it, because in that case they would have lost the prey which God had allowed them. Indeed, it is evident from verse

28, that the main part of the city was not burned till after the battle, and they had taken out all the cattle and other spoils that were therein. The people that fled turned back That is, the Israelites, who had counterfeited a flight, turned upon the men of Ai, who pursued them. The other issued out of the city Namely, those who lay in ambush, and were now in possession of the city. The king they took alive Reserved him to a more ignominious death.