Deuteronomy 13:3-4

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