Deuteronomy 18:21-22

21And if you say in your heart, ‘How may we know the word that the  Lord has not spoken?’— 22 awhen a prophet speaks in the name of the  Lord, if the word does not come to pass or come true, that is a word that the  Lord has not spoken; bthe prophet has spoken it presumptuously. You need not be afraid of him.

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