Deuteronomy 18:21-22

American Standard Version

²¹ And if thou say in thy heart, How shall we know the word which Jehovah hath not spoken? ²² when a prophet speaketh in the name of Jehovah, if the thing follow not, nor come to pass, that is the thing which Jehovah hath not spoken: the prophet hath spoken it presumptuously, thou shalt not be afraid of him.