What does 2 Chronicles 13:12 mean?

Look, God himself is with us, leading us, and his priests are ready to blow the trumpets to sound the alarm against you. People of Israel, don't fight against the Lord, the God of your ancestors, because you won't win. 2 Chronicles 13:12 - Modern Text Bible

(Abijah warns them that fighting Judah is really fighting God, and that's a battle they can't win.)