Deuteronomy 13:5-9

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

6If thy brother, the son of thy mother, or thy son, or thy daughter, or the wife of thy bosom, or thy friend, that is as thine own soul, entice thee secretly, saying, Let us go and serve other gods, which thou hast not known, thou, nor thy fathers; 7of the gods of the peoples that are round about you, nigh unto thee, or far off from thee, from the one end of the earth even unto the other end of the earth; 8thou shalt not consent unto him, nor hearken unto him; neither shall thine 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.