Deuteronomy 18:20

But the prophet which shall presume to speak in my name
Pretending a mission and commission from God, and yet was never sent by him, like the prophets in ( Jeremiah 23:21 ) ,

which I have not commanded him to speak;
which though true was not to be spoken in a public manner, by assuming a public office, without a divine authority or a commission from God, and much less what was false, and never commanded to be spoken at all by any:

or, that shall speak in the name of other gods;
the idols of the people, as the Targum; as if any should affirm they were sent by Jove, or inspired by Apollo, as some are said to prophesy by Baal, as if they had received their orders and instructions from him, and were inspired by him, ( Jeremiah 2:8 )

even that prophet shall die;
the Targum of Jonathan is, be killed by the sword, but the Jews ^F17 generally interpret it of strangling.