וְכָל־מוֹאָב֙ שָֽׁמְע֔וּ כִּֽי־עָל֥וּ הַמְּלָכִ֖ים לְהִלָּ֣חֶם בָּ֑ם וַיִּצָּעֲק֗וּ מִכֹּ֨ל חֹגֵ֤ר חֲגֹרָה֙ וָמַ֔עְלָה וַיַּעַמְד֖וּ עַֽל־הַגְּבֽוּל׃
Now when all the Moabites heard that the kings were come up to fight against them, they gathered themselves together, all that were able to put on armour, and upward, and stood on the border.
Read halakhic rulings (Jewish law) on II Kings 3:21 from the Mishneh Torah and classical halakhic sources, free online.