21 And when he had consulted with the people, he appointed those who should sing to the Lord, and who should praise the beauty of holiness, as they went out before the army and were saying: "Praise the Lord, For His mercy endures forever." 22 Now when they began to sing and to praise, the Lord set ambushes against the people of Ammon, Moab, and Mount Seir, who had come against Judah; and they were defeated. 23 For the people of Ammon and Moab stood up against the inhabitants of Mount Seir to utterly kill and destroy them. And when they had made an end of the inhabitants of Seir, they helped to destroy one another. 24 So when Judah came to a place overlooking the wilderness, they looked toward the multitude; and there were their dead bodies, fallen on the earth. No one 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.