לְמַ֗עַן אֲשֶׁ֨ר לֹֽא־יְלַמְּד֤וּ אֶתְכֶם֙ לַעֲשׂ֔וֹת כְּכֹל֙ תּֽוֹעֲבֹתָ֔ם אֲשֶׁ֥ר עָשׂ֖וּ לֵֽאלֹהֵיהֶ֑ם וַחֲטָאתֶ֖ם לַיהוָ֥ה אֱלֹהֵיכֶֽם׃ (ס)
that they teach you not to do after all their abominations, which they have done unto their gods, and so ye sin against the LORD your God.
Read halakhic rulings (Jewish law) on Deuteronomy 20:18: and classical halakhic sources.