וְאִם־תְּמָאֲנ֖וּ וּמְרִיתֶ֑ם חֶ֣רֶב תְּאֻכְּל֔וּ כִּ֛י פִּ֥י יְהוָ֖ה דִּבֵּֽר׃ (ס)
But if ye refuse and rebel, Ye shall be devoured with the sword; For the mouth of the LORD hath spoken.
Read halakhic rulings (Jewish law) on Isaiah 1:20: and classical halakhic sources.