C. F. Keil and Franz Delitzsch on 2 Chronicles 20:20-21

2Ch 20:20-21

The fulfilment of the divine promise. - 2Ch 20:20. On the next morning the assembled men of Judah marched, in accordance with the words of the prophet, to the wilderness of Tekoa. As they marched forth, Jehoshaphat stood, probably in the gate of Jerusalem, where those about to march forth were assembled, and called upon them to trust firmly in the Lord and His prophets (האמינוּ and תּאמנוּ, as in Isa 7:9). After he had thus counselled the people (אל יוּעץ, shown himself a counsellor; cf. 2Ki 6:8), he ordered them to march, not for battle, but to assure themselves of the wonderful help of the Lord. He placed singers of the Lord (ל before יהוה as a periphrasis for the genitive), singing praise in holy ornaments, in the marching forth before the army, and saying; i.e., he commanded the Levitic singers to march out before the army, singing and playing in holy ornaments (להדרת־ק, clad in holy ornaments, = בּהדרת in 1Ch 16:29; cf. Ew. §217, a), to praise the Lord for the help He had vouchsafed.