Deuteronomy 18:20-22

20 "But any prophet who fakes it, who claims to speak in my name something I haven't commanded him to say, or speaks in the name of other gods, that prophet must die."

21 You may be wondering among yourselves, "How can we tell the difference, whether it was God who spoke or not?" Here's how:

22 If what the prophet spoke in God's name doesn't happen, then obviously God wasn't behind it; the prophet made it up. Forget about him.

Deuteronomy 18:20-22 Meaning and Commentary

INTRODUCTION TO DEUTERONOMY 18

This chapter gives an account of the provision made for the priests and Levites, with the reason of it, De 18:1-5, of allowance of a country Levite to minister at Jerusalem, and take his portion with the rest, De 18:6-8, and of several persons of bad practices not to be suffered among the people of Israel, De 18:9-14, and of an extraordinary prophet that should be raised up among them, to whom they should hearken, or it would be the worse for them, De 18:15-19, but a false prophet was to be put to death, of whom a sign is given by which he might be known, De 18:20-22.