15 And he said, Give ear, O Judah, and you people of Jerusalem, and you, King Jehoshaphat: the Lord says to you, Have no fear and do not be troubled on account of this great army; for the fight is not yours but God's. 16 Go down against them tomorrow: see, they are coming up by the slope of Ziz; at the end of the valley, before the waste land of Jeruel, you will come face to face with them. 17 There will be no need for you to take up arms in this fight; put yourselves in position, and keep where you are, and you will see the salvation of the Lord with you, O Judah and Jerusalem: have no fear and do not be troubled: go out against them tomorrow, for the Lord is with you.
Matthew Henry's Commentary on 2 Chronicles 20:15-17
Commentary on 2 Chronicles 20:14-19
(Read 2 Chronicles 20:14-19)
The Spirit of prophecy came upon a Levite in the midst of the congregation. The Spirit, like the wind, blows where and on whom He listeth. He encouraged them to trust in God. Let the Christian soldier go out against his spiritual enemies, and the God of peace will make him more than a conqueror. Our trials will prove our gain. The advantage will be all our own, but the whole glory must be given to God.