Adam Clarke on 2 Kings 3:19

Shall fell every good tree - Every tree by which your enemies may serve themselves for fortifications, etc. But surely fruit trees are not intended here; for this was positively against the law of God, Deu 20:19, Deu 20:20 : "When thou shalt besiege a city - thou shalt not destroy the trees thereof - for the tree of the field is man's life - only the trees which thou knowest that they be not trees for meat, thou shalt destroy and cut them down."

Stop all wells of water - In those hot countries this would lead sooner than any thing else to reduce an enemy.

Mar every good piece of land with stones - Such a multitude of men, each throwing a stone on a good field as they passed, would completely destroy it.