Deuteronomy 13:9

Deuteronomy 13 warns that even a prophet or dreamer whose sign comes to pass must be put to death if he urges Israel to follow other gods, because the Lord is testing their love for Him. It likewise commands that a near relative or friend who secretly entices them to idolatry must be shown no pity but put to death, and that an entire city turned to idolatry must be utterly destroyed and burned, its spoil heaped up never to be rebuilt. Through such judgment Israel would learn to fear the Lord and keep His commandments.