“You may say to yourselves, ‘How can we know when a message has not been spoken by the Lord?’ If what a prophet proclaims in the name of the Lord does not take place or come true, that is a message the Lord has not spoken. That prophet has spoken presumptuously, so do not be alarmed”

Deuteronomy 18:21-22

“But a prophet who presumes to speak in my name anything I have not commanded...is to be put to death”

Deuteronomy 18:20

Not saying here that we should kill todays false prophets, just that God gave a standard to adjudicate between true and false prophets.