Deuteronomy 13:6-9

6If your very own brother, or your son or daughter, or the wife you love, or your closest friend secretly entices you, saying, “Let us go and worship other gods” (gods that neither you nor your ancestors have known, 7gods of the peoples around you, whether near or far, from one end of the land to the other), 8do not yield to them or listen to them. Show them no pity. Do not spare them or shield them. 9You must certainly put them to death. Your hand must be the first in putting them to death, and then the hands of all the people.