Deuteronomy 18:21-22

Darby Translation

²¹ And if thou say in thy heart, How shall we know the word that Jehovah hath not spoken?

²² When a prophet speaketh in the name of Jehovah, and the thing followeth not, nor cometh to pass, that is the word which Jehovah hath not spoken; the prophet hath spoken it presumptuously: be not afraid of him.