Deuteronomy 18:20-22

International Standard Version

²⁰ Even then, if the prophet speaks presumptuously in my name, which I didn’t authorize him to speak, or if he speaks in the name of other gods, that prophet must die.’ ²¹ Now you may ask yourselves, ‘How will we be able to discern that the Lord has not spoken?’ ²² Whenever a prophet speaks in the name of the Lord and the oracle does not come about or the word is not fulfilled, then the Lord has not spoken it. The prophet will have spoken presumptuously, so you need not fear him.”