John Gill Bible Commentary

And they beat down the cities,.... Demolished the walls of them, and houses in them, wherever they came: and on every good piece of land cast every man his stone, and filled it; which they had taken out of the walls and houses they pulled down; or which they picked up in the highway, as they passed along, being a stony country; or which being laid in heaps, gathered out of the fields, they took and scattered them all over them: and they stopped all the wells of water; with stones and dirt: and felled all the good trees; fruit bearing ones; See Gill on Kg2 3:19, only in Kirharaseth left they the stones thereof; not able to demolish it, it being a strong fortified city, the principal of the kingdom, and into which the king of Moab had thrown himself, and the remains of his forces; of which see Isa 16:7, howbeit, the slingers went about it, and smote it; smote the soldiers that appeared upon the walls of it; though Kimchi, and other Jewish writers, understand it of engineers, who cast out large stones from a sort of machines then in use, to batter down and break through the walls of cities.