Albert Barnes 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)

If the present text is regarded as sound, this passage must be taken ironically. But most recent commentators supply a second negative and render it: “But go you alone, act, be strong for the battle—God shall then not make you to fall.”