Deuteronomy 13:1-3

If a prophet, or one who foretells by dreams, appears among you and announces to you a sign or wonder, and if the sign or wonder spoken of takes place, and the prophet says, “Let us follow other gods” (gods you have not known) “and let us worship them,” you must not listen to the words of that prophet or dreamer. The LORD your God is testing you to find out whether you love him with all your heart and with all your soul.