21 And when he had taken counsel with the people, he appointed those who were to sing to the Lord and praise him in holy array, as they went before the army, and say, "Give thanks to the Lord, for his steadfast love endures for ever." 22 And when they began to sing and praise, the Lord set an ambush against the men of Ammon, Moab, and Mount Se'ir, who had come against Judah, so that they were routed. 23 For the men of Ammon and Moab rose against the inhabitants of Mount Se'ir, destroying them utterly, and when they had made an end of the inhabitants of Se'ir, they all helped to destroy one another. 24 When Judah came to the watchtower of the wilderness, they looked toward the multitude; and behold, they were dead bodies lying on the ground; none 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.