Deuteronomy 18:20

18:20 But the prophet, who shall speak a word presumptuously in my name, which I have not commanded him to speak, or who shall speak in the name of other gods, that same prophet shall die.
-World English Bible

Other Translation

18:20 But the prophet, which shall presume to speak a word in my name, which I have not commanded him to speak, or that shall speak in the name of other gods, even that prophet shall die.
-King James Version