Deuteronomy 18:20-22

20But any prophet who dares to say something in my name that I didn’t command him to say or who speaks in the name of other gods must die.”

21You may be wondering, “How can we recognize that the Lord didn’t speak this message?”

22If a prophet speaks in the Lord’s name and what he says doesn’t happen or come true, then it didn’t come from the Lord. That prophet has spoken on his own authority. Never be afraid of him.