Deuteronomy 13:6-9

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 to thee as thy soul, entice thee secretly, saying, Let us go and serve other 1gods (whom thou hast not known, thou, nor thy fathers;

7of the 2gods of the peoples which are round about you, near unto thee, or far from thee, from 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 spare him, neither shalt thou pity him, neither shalt thou screen him,

9but thou shalt in any case kill him: thy hand shall be the first against him to put him to death, and afterwards the hands of all the people;