Deuteronomy 18:20

18:20 “But if any prophet presumes to speak anything in my name that I have not authorized ¹  him to speak, or speaks in the name of other gods, that prophet must die.

Jeremiah 28:15-17

28:15 Then the prophet Jeremiah told the prophet Hananiah, “Listen, Hananiah! The Lord did not send you! You are making these people trust in a lie! ²  28:16 So the Lord says, ‘I will most assuredly remove ³  you from the face of the earth. You will die this very year because you have counseled rebellion against the Lord.’” ⁴ 

28:17 In the seventh month of that very same year ⁵  the prophet Hananiah died.

[18:20]  ¹ tn Or “commanded” (so KJV, NAB, NIV, NRSV).

[28:15]  ² tn Or “You are giving these people false assurances.”

[28:16]  ³ sn There is a play on words here in Hebrew between “did not send you” and “will…remove you.” The two verbs are from the same root word in Hebrew. The first is the simple active and the second is the intensive.

[28:16]  ⁴ sn In giving people false assurances of restoration when the Lord had already told them to submit to Babylon, Hananiah was really counseling rebellion against the Lord. What Hananiah had done was contrary to the law of Deut 13:6 and was punishable by death.

[28:17]  ⁵ sn Comparison with Jer 28:1 shows that this whole incident took place in the space of two months. Hananiah had prophesied that the captivity would be over before two years had past. However, before two months were past, Hananiah himself died in fulfillment of Jeremiah’s prophecy of his death. His death was a validation of Jeremiah as a true prophet. The subsequent events of 588 b.c. would validate Jeremiah’s prophesies and invalidate those of Hananiah.