Deuteronomy 5:11

5:11 You must not make use of the name of the Lord your God for worthless purposes, for the Lord will not exonerate anyone who abuses his name that way.

Deuteronomy 18:20

18:20 “But if any prophet presumes to speak anything in my name that I have not authorized him to speak, or speaks in the name of other gods, that prophet must die.