וַיִּקְבֹּ֨ץ מֶֽלֶךְ־יִשְׂרָאֵ֥ל אֶֽת־הַנְּבִאִים֮ אַרְבַּ֣ע מֵא֣וֹת אִישׁ֒ וַיֹּ֣אמֶר אֲלֵהֶ֗ם הֲנֵלֵ֞ךְ אֶל־רָמֹ֥ת גִּלְעָ֛ד לַמִּלְחָמָ֖ה אִם־אֶחְדָּ֑ל וַיֹּאמְר֣וּ עֲלֵ֔ה וְיִתֵּ֥ן הָאֱלֹהִ֖ים בְּיַ֥ד הַמֶּֽלֶךְ׃
Then the king of Israel gathered the prophets together, four hundred men, and said unto them: ‘Shall we go to Ramoth-gilead to battle, or shall I forbear?’ And they said: ‘Go up; for God will deliver it into the hand of the king.’
Read midrashic interpretation of II Chronicles 18:5: and classical rabbinic exegesis.