21 After consulting the people, the king appointed singers to walk ahead of the army, singing to the Lord and praising him for his holy splendor. This is what they sang: "Give thanks to the Lord ; his faithful love endures forever!" 22 At the very moment they began to sing and give praise, the Lord caused the armies of Ammon, Moab, and Mount Seir to start fighting among themselves. 23 The armies of Moab and Ammon turned against their allies from Mount Seir and killed every one of them. After they had destroyed the army of Seir, they began attacking each other. 24 So when the army of Judah arrived at the lookout point in the wilderness, all they saw were dead bodies lying on the ground as far as they could see. Not a single one of the enemy had escaped.
Matthew Henry's Commentary on 2 Chronicles 20:21-24
Commentary on 2 Chronicles 20:20-30
(Read 2 Chronicles 20:20-30)
Jehoshaphat exhorted his troops to firm faith in God. Faith inspires a man with true courage; nor will any thing help more to the establishing of the heart in shaking times, than a firm belief of the power, and mercy, and promise of God. In all our trust in the Lord, and our praises of him, let us especially look at his everlasting mercy to sinners through Jesus Christ. Never was an army so destroyed as that of the enemy. Thus God often makes wicked people destroy one another. And never was a victory celebrated with more solemn thanksgivings.