Deuteronomy 18:19-22

191It shall come about that whoever will not listen to My words which he shall speak in My name, I Myself will require it of him.

20But the prophet who speaks a word 2presumptuously in My name which I have not commanded him to speak, or 3which he speaks in the name of other gods, 4that prophet shall die.’

215You may say in your heart, ‘How will we know the word which the Lord has not spoken?’

226When a prophet speaks in the name of the Lord, if the thing does not come about or come true, that is the thing which the Lord has not spoken. The prophet has spoken it 7presumptuously; you shall not be afraid of him.