Deuteronomy 13:5-9

5And that prophet, or that dreamer of dreams, shall be put to death; because he hath spoken to turn you away from the LORD your God, who brought you out of the land of Egypt, and redeemed you from the house of bondage, to thrust thee out of the way which the LORD thy God commanded thee to walk in. So shalt thou remove the evil from the midst of thee.1

6If thy brother, the son of thy mother, or thy son, or thy daughter, or the wife of thy bosom, or thy friend, who is as thy own soul, shall entice thee secretly, saying, Let us go and serve other gods, which thou hast not known, thou, nor thy fathers; 7Namely, of the gods of the people who are around you, near to thee, or far off from thee, from one end of the earth even to the other end of the earth; 8Thou shalt not consent to him, nor hearken to him; neither shall thy eye pity him, neither shalt thou spare, neither shalt thou conceal him: 9But thou shalt surely kill him; thy hand shall be first upon him to put him to death, and afterwards the hand of all the people.