You need not fight this battle. Take up your positions, stand firm, and see the salvation of the LORD on your behalf, O Judah and Jerusalem. Do not be afraid or discouraged. Go out and face them tomorrow, for the LORD is with you.’”
We have here God's gracious answer to Jehoshaphat's prayer; and it was a speedy answer. While he was yet speaking God heard: before the congregation was dismissed they had assurance given them that they should be victorious; for it is never in vain to seek God. 1.
Commenting on 2 Chronicles 20:14-19
Ye shall not need to fight in this battle,.... Since the Lord would fight for them: set yourselves, stand ye still; present themselves they might, as if ready to engage; and keep their ground, not giving way in the least, but would have no need to strike a stroke: and see the salvation of the Lord with you; which he would work for them, see...
For the Lord will be with you - "The Word of the Lord shall be your Helper." - Targum.