Deuteronomy 13:1-3

If there arise in the midst of thee a prophet, or a dreamer of dreams, and he give thee a sign or a wonder, and the sign or the wonder come to pass, whereof he spake unto thee, saying, Let us go after other gods, which thou hast not known, and let us serve them; thou shalt not hearken unto the words of that prophet, or unto that dreamer of dreams: for Jehovah your God proveth you, to know whether ye love Jehovah your God with all your heart and with all your soul.