Deuteronomy 13:6 (KJV)

Ye shall walk after the Lord your God, and fear him, and keep his commandments, and obey his voice, and ye shall serve him, and cleave unto him.

And 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, which brought you out of the land of Egypt, and redeemed you out of the house of bondage, to thrust thee out of the way which the Lord thy God commanded thee to walk in. So shalt thou put the evil away from the midst of thee.

If thy brother, the son of thy mother, or thy son, or thy daughter, or the wife of thy bosom, or thy friend, which 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;

Namely, of the gods of the people which 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;

Thou shalt not consent unto him, nor hearken unto him; neither shall thine eye pity him, neither shalt thou spare, neither shalt thou conceal him: