Deuteronomy 18:21-22

Amplified Bible, Classic Edition

²¹ And if you say in your [minds and] hearts, How shall we know which words the Lord has not spoken?

²² When a prophet speaks in the name of the Lord, if the word does not come to pass or prove true, that is a word which the Lord has not spoken. The prophet has spoken it presumptuously; you shall not be afraid of him.