Deuteronomy 13:12-15

12"If you hear in one of your cities, which the Lord your God is giving you to dwell there,

13that certain worthless fellows have gone out among you and have drawn away the inhabitants of their city, saying, 'Let us go and serve other gods,' which you have not known,

14then you shall inquire and make search and ask diligently. And behold, if it be true and certain that such an abomination has been done among you,

15you shall surely put the inhabitants of that city to the sword, devoting it to destruction, all who are in it and its cattle, with the edge of the sword.