Hamstringing involved cutting the connecting tendon in the hind leg of the horse, thereby disabling its running ability.1 Israel would thus not be able to use the horses for themselves, nor would their enemies be able to use them. Hamstringing was an exception to the general treatment of animals in Israel; wild and domestic animals were to be treated with care (Genesis 9:12; Deuteronomy 5:14; Deuteronomy 25:4).2 By burning the chariots (which were made of wood), the temptation for Israel to use them is removed. They were to trust in the Lord to fight for them and protect them, not in military armaments (Psalm 20:7).3
6 And the LORD said to Joshua, “Do not be afraid of them, for tomorrow at this time I will give over all of them, slain, to Israel. You shall hamstring their horses and burn their chariots with fire.”