“And when you say in your heart, How do we know the word which YHWH has not spoken?”— Deuteronomy 18:21 (LSV)
18I raise up for them a Prophet like you out of the midst of their brothers, and I have given My words in His mouth, and He has spoken to them all that which I command Him;
19and it has been [that] the man who does not listen to My words which He speaks in My Name, I require [it] of him.
20Only, the prophet who presumes to speak a word in My Name, which I have not commanded him to speak, and who speaks in the name of other gods, indeed, that prophet has died.
21And when you say in your heart, How do we know the word which YHWH has not spoken?
22That which the prophet speaks in the Name of YHWH, and the thing is not, and does not come—it [is] the word which YHWH has not spoken; the prophet has spoken it in presumption; you are not afraid of him.”