John Gill Commentary Deuteronomy 3:22

"Ye shall not fear them; for Jehovah your God, he it is that fighteth for you." — Deuteronomy 3:22 (ASV)

You shall not fear them
On account of the numbers, strength, courage, and gigantic stature of the inhabitants, at least some of them; nor on account of their walled towns, and fortified cities:

for the Lord your God he shall fight for you ;
as he did, particularly at Jericho, the walls of which city fell at the sound of rams' horns; and at Gibeon, when he cast down hailstones on their enemies, and more were slain by them than with the sword; and in all their battles it was he that gave them success and victory.