Deuteronomy 18:20-22

20But the prophet who speaks a word 1presumptuously in My name, a word which I have not commanded him to speak, or 2which he speaks in the name of other gods, 3that prophet shall die.’

21And if you say in your heart, ‘How will we recognize the word which the Lord has not spoken?’

224When the prophet speaks in the name of the Lord, and the thing does not happen or come true, that is the thing which the Lord has not spoken. The prophet has spoken it 5presumptuously; you are not to be afraid of him.