1 Kings 12:21

And when Rehoboam was come to Jerusalem, he assembled all the house of Judah, with the tribe of Benjamin, an hundred and fourscore thousand chosen men, which were warriors, to fight against the house of Israel, to bring the kingdom again to Rehoboam the son of Solomon.

Cross-reference

2 Chronicles 11:1-3 parallels Rehoboam's war assembly and adds that God forbade the fight through Shemaiah.

Proverbs 21:31 states that victory belongs to the Lord despite preparation — Rehoboam’s army cannot guarantee success.