2 Chronicles 20:21

And when he had consulted with the people
His principal officers, in what order they should march, and in what manner they should form themselves, when they met the enemy, and how they should conduct as if they were to engage: he appointed singers unto the Lord;
to sing his praise, and give him glory, as if the victory was already completed, it being so sure: and that should praise the beauty of holiness, as they went out before
the army;
that is, praise God, who is glorious in holiness, whose beauty lies in his holiness, and who is holy in all his ways and works: and to say, praise the Lord, for his mercy endureth for ever;
with which they were to conclude their songs of praise, as David did, and whose songs they might sing; see ( Psalms 136:1-26 ) .