Талмуд к Бамидбар 33:49

It was stated: A student who gave instructions about practice in front of his teacher has committed a deadly sin²⁵Babli Berakhot 31b, Eruvin 63a, Yerushalmi Giṭṭin 1:2. This insert takes up the theme of unauthorized ruling from the previous story. However, in the previous case it was assumed that the student was not ordained; he is prohibited from giving instructions by a late rabbinic ordinance. In the present paragraph the student is ordained; nevertheless, he may not issue instructions at his teacher’s place by a Biblical injunction. (The story of Rebbi at Acco is continued in the next paragraph.). It was stated in the name of Rebbi Eliezer: Nadab and Abihu died only because they determined practice in the presence of their teacher Moses²⁶They died because they presented “a strange fire that was not commanded to them.” Since they must have had some rationale for their actions, it follows that they acted on their own judgment, not consulting their teacher Moses. Since Moses was not with them at that moment, it also follows that “in front of his teacher” means “while his teacher is alive”, in that case, in the encampment of the Israelites in the desert. Their argument is hinted at in Babli Yoma 53a.. It happened that a student gave instructions about practice in front of his teacher Rebbi Eliezer. The latter said to his wife Imma Shalom²⁷The sister of Rabban Gamliel. The parallel is in Babli Eruvin 63a; there R. Eliezer speaks of a year, not a week.: That one will not live out his week. The week was not completed when he died. His students said to him: Rebbi, you are a prophet. He said to them (Amos 7:14) “I am neither a prophet nor the disciple of a prophet” but I have received a tradition that any student who gives instructions about practice in front of his teacher has committed a deadly sin. It was stated: A student is forbidden to give instructions about practice during the lifetime of his teacher unless he be at a distance of at least 12 mil from him, [the breadth of] the camp of Israel. What is the reason? (Num. 33:49) “They encamped along the Jordan from Bet Hayyešimot to Abel Haššiṭṭim”; how far is this? Twelve mil²⁸In the Babli (Eruvin 55b,Yoma75b) this is a determination of Rabba bar bar Ḥana. The text here shows that in the Babli the reading “3 parasangs” (12 mil) of the mss. is to be preferred over “3 parasangs square” of the Venice edition, against the opinion of R. Rabbinovicz (Diqduqe Soferim Eruvin p. 224, Note.פ ) A mil is 2000 cubits, cf. Kilaim Chapter 5, Note 25.. Like this: Rebbi Tanḥum ben Ḥiyya was in Ḥefer²⁹The Biblical Gat Ḥefer, possibly the village El-Mešad near Kafr Kanna, not far from Sepphoris.; they asked him repeatedly and he gave instructions about practice. They said to him, did the rabbi not teach us that a student may not give instructions about practice during the lifetime of his teacher unless he be at a distance of at least 12 mil from him, [the breadth of] the camp of Israel; and your teacher Rebbi Mana sits at Sepphoris! He said to them, so it should come over me that I did not know! From that moment on he did no longer give instructions.