Charles Ellicott Commentary 2 Chronicles 25:8

"But if thou wilt go, do [valiantly], be strong for the battle: God will cast thee down before the enemy; for God hath power to help, and to cast down." — 2 Chronicles 25:8 (ASV)

But if you will go. —Rather, But go yourself; in contrast with the prohibition, Let not the army of Israel go.

Do it, be strong for the battle. —Compare 1 Chronicles 22:16: Arise! act!

God shall make you fall. —Before these words, the expression wĕlô’, “and not,” must have dropped out of the text. “Venture on the expedition by yourself with good courage,” says the prophet, “and God will not let you stumble before the foe.”

For God has power. — For there is strength in God, to help and to make to stumble. (Compare 2 Chronicles 20:6; 1 Chronicles 29:12; Psalms 9:3.)

The ancient versions were evidently embarrassed by the passage. The Septuagint renders: “Because if you think to prevail through them, then will the Lord rout you before your foes; because it is from the Lord both to be strong and to rout.”

The Vulgate renders: “But if you think that wars depend on the strength of an army, God will make you to be overcome by the enemy.”

The Syriac renders: “Because you are going to make war, the Lord will cast you down before your foes; because you have not praised the Lord, who is the helper and uplifter.”

It is noticeable that no version inserts the required negative; the omission, therefore, is ancient.