Deuteronomy 18:21

I will raise them up a prophet from among their brothers, like you. I will put my words in his mouth, and he shall speak to them all that I shall command him.

It shall happen, that whoever will not listen to my words which he shall speak in my name, I will require it of him.

But the prophet who speaks a word presumptuously in my name, which I have not commanded him to speak, or who speaks in the name of other gods, that same prophet shall die.”

When a prophet speaks in the LORD’s name, if the thing doesn’t follow, nor happen, that is the thing which the LORD has not spoken. The prophet has spoken it presumptuously. You shall not be afraid of him.