Deuteronomy 18:21–22
21 And if you say in your heart, ‘How may we know the word that 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 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.
Ezekiel 33:33
33 aWhen this comes—and come it will!—then bthey will know that a prophet has been among them.”