פירוש על דברי הימים ב 20:17

set yourself This refers back to (verse 15) “for the war is not yours.”

and see the salvation of the Lord This refers back to the above: “Have You, our God, not caused us to inherit (sic)?” And the Holy One, blessed be He, said to them, “You are right. It is up to Me to preserve it in your hands.”

Tomorrow go forth before them and I shall wage war on your behalf. And they believed, and hurried, and arose early in the morning.