וַיֵּצֵ֥א הָעָ֛ם הַשָּׂדֶ֖ה לִקְרַ֣את יִשְׂרָאֵ֑ל וַתְּהִ֥י הַמִּלְחָמָ֖ה בְּיַ֥עַר אֶפְרָֽיִם׃
So the people went out into the field against Israel; and the battle was in the forest of Ephraim.
Read halakhic rulings (Jewish law) on II Samuel 18:6: and classical halakhic sources.