Deuteronomy 18:21-22

Deuteronomy 18:21-22 ESV

And if you say in your heart, ‘How may we know the word that the LORD has not spoken?’— when 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; the prophet has spoken it presumptuously. You need not be afraid of him.
ESV: English Standard Version 2016