Midrash su Deuteronomio 18:19

(Fol. 75a) R. Zutra b. Tubia in the name of Rab said: "He who pulls the thread of a seam on the Sabbath [bringing both ends closer together and preventing it from going asunder] is bound to bring a sin-offering [for his act]; he who learns one thing [even a matter of law] from an Amgusha deserves to be punished with death; and he who understands the science of astronomy and does not make use of it, is not worth being spoken of." What is Amgusha? Rab and Samuel differ: one declares it to mean a sorcerer, the other contends that it means a blasphemer. It may be ascertained that Rab is the one who said a blasphemer; for R. Zutra b. Tubia said in the name of Rab: "He who learns one thing [even a matter of law] from an Amgusha deserves to be punished with death," and if we assume that Rab said a sorcerer, then why should a man who learns from him deserve death? Behold, it is written (Deu. 18, 19.) Thou shalt not learn to do, but thou mayest learn to understand and to judge. [We must therefore say that Rab declared it to mean a blasphemer.] The assertion is sustained.

(Devarim 18:19) "And it shall be, the man who will not heed My words": There are three whose death is at the hands of Heaven: one who suppresses his prophecy, like Yonah the son of Amittai; one who dismisses the words of a prophet, as did the colleague of Michah (viz. I Kings 20:35), and a prophet who transgresses his own prophecy, as did Iddo, viz. (I Kings 13:21). And there are three whose death is at the hands of beth-din: one who prophesies what he did not hear (from G-d), like Tzidkiyahu ben Cna'anah (viz. I Kings 22:24); and what was not spoken to him, like Chananiah ben Azur, who heard things from the mouth of Jeremiah, who prophesied in the upper marketplace and went and prophesied in the lower marketplace (viz. Jeremiah 28); and one who prophesies in the name of idolatry, i.e., "This is what the idol says" — even if what he said was consistent with the halachah, to rule unclean what was unclean, and clean what was clean — it being written (Ibid. 20) "But the prophet who shall presume, etc."