Deuteronomy 18:20-22
20‘But the prophet who speaks a word apresumptuously in My name which I have not commanded him to speak, or bwhich he speaks in the name of other gods, 1that prophet shall die.’ 21“Now 1you may say in your heart, ‘How will we know the word which Yahweh has not spoken?’ 22“aWhen a prophet speaks in the name of Yahweh, if the thing does not come about or come true, that is the thing which Yahweh has not spoken. The prophet has spoken it bpresumptuously; you shall not be afraid of him.