Deuteronomy 13:4 "Do not listen to the words of that prophet"

This Negative Mitzvah cautions us not to heed the words of a false prophet.

The Torah itself has given us specific guidelines so that we may distinguish a true prophet from a false one.

If a person prophesies in the name of an idol we are commanded not to listen to him, nor demand any proof or signs from him.

Once the name of an idol or another G‑d is mentioned, that, itself, proves to us that the individual is a false prophet.