ויבאו [וַיָּבֹ֣א] רְחַבְעָם֮ יְרוּשָׁלִַם֒ וַיַּקְהֵל֩ אֶת־כָּל־בֵּ֨ית יְהוּדָ֜ה וְאֶת־שֵׁ֣בֶט בִּנְיָמִ֗ן מֵאָ֨ה וּשְׁמֹנִ֥ים אֶ֛לֶף בָּח֖וּר עֹשֵׂ֣ה מִלְחָמָ֑ה לְהִלָּחֵם֙ עִם־בֵּ֣ית יִשְׂרָאֵ֔ל לְהָשִׁיב֙ אֶת־הַמְּלוּכָ֔ה לִרְחַבְעָ֖ם בֶּן־שְׁלֹמֹֽה׃ (פ)
And when Rehoboam was come to Jerusalem, be assembled all the house of Judah, and the tribe of Benjamin, a hundred and fourscore thousand chosen men that were warriors, to fight against the house of Israel, to bring the kingdom back to Rehoboam the son of Solomon.
Read halakhic rulings (Jewish law) on I Kings 12:21: and classical halakhic sources.