Moreh Lifnei Rabbo

This is from a pre-internet journal I used to keep. 

The Se’ir Rosh Chodesh of Aharon.  (5759-1999) Dr. Krinsky asked me, how is it possible that immediately after the death of Nadav and Avihu, which according to some was for paskening lifnei rabban, that Aharon burned the korbon of Rosh chodesh without asking Moshe!  And you can’t answer that to Aharon it was even more poshut than bei’asah be’kutcha, because we see that Moshe didn’t realize that Aharon was right at first.  So I told Dr. Krinsky that maybe Aharon wasn’t a talmid, or at least that he was a talmid chover.  But then I turned to Moshe, who hadn’t heard the conversation, and asked him whether he thought that Aharon was considered a talmid of Moshe, or was he an equal.  Moshe answered, “Aharon must have been an equal to Moshe, because if he wasn’t, he wouldn’t have burned the se’ir Rosh Chodesh without asking Moshe.”  Dr. Krinsky couldn’t believe that Moshe hadn’t heard our conversation, but the fact is, he hadn’t.

 (5760-2000).  I checked the sforim, and it turns out that both Reb Moshe and the Lutzker Rov ask the question-- but the Lutzker Rov on 10:19 asks on Aharon, and so he says that Moshe and Aharon were ‘shkulim’, as above; Reb  Moshe, on the other hand, asks the question on Elozor and Isomor (in the first Dorash Moshe, on 10:20,) and he answers that since Rashi says that Moshe admitted that he learned the drosho of Aharon from Hashem but forgot it, this shows that he had taught it to them, and so there was no halacha of moreh lifnei rabbon
 I asked the kids the question again this year, and both Mordechai and Ita showed me the Rashi  in 10:19 that says that the reason Aharon answered Moshe, when Moshe had directed his question to Elozor and Isomor, was that it would not be appropriate for a talmid to respond to his rebbi’s tayneh.  This, they said, shows that while Elozor and Isomor were considered Moshe’s talmidim, Aharon was not.
 I also saw the Ohr Hachaim, who says that Aharon’s drosho from Maiser is so clear, that this din has a halacha of ‘bei’aso bekutcho.’
 (August 2000/5760) I saw the Mishneh in Avos 4:12, and the Machzor Vitri’s pirush there, and the Avos D’rav Nosson towards the end of Perek 27 and the pirush of the Ben Avrohom there.  The bottom line is, that almost everyone says that Moshe was the rebbi (obviously, and as the Gemora in Eruvin 54b says,) but since Aharon was older, they were considered ‘shkulim’.  This doesn’t, however, affect the fact that Moshe was the Rebbi, and there should be a halocho of moreh lifnei rabbo.  Also— the Medrash Rabba in Shemos 3:17 says, on “ve’atta tihiyeh lo leilohim”, that even though Aharon was older, since Moshe was the rebbi, Aharon had to be mechabed Moshe like he was mechabed the Shechina (moreh Rabboch kimoreh shomayim.)
 (February ‘03/Adar I ‘63) I saw that the Netziv in the beginning of Parshas Tetzaveh (Shemos 27:20) says, after bringing several of the aforementioned rayos, that Aharon did not have a din of a talmid.  Although he did learn from Moshe, after he learned from Moshe he did not need him, and he was considered an equal gadol.  However, Moshe’s gadlus was in pilpul and chiddush, while Aharon’s was in svoro yeshoro and emes, ‘lehoros es Bnei Yisroel.’  And then he brings that this advantage of Aharon in svoro yeshoro resulted in Aharon’s ascension over Moshe when Aharon paskened correctly regarding the Se’ir Rosh Chodesh

UPDATE APRIL 2025/NISSAN '85)   Avi Saltzman said Aharon had the excuse of being an Onein. He didn't explain his question, but I suppose he meant thae Gemara BB 16b on Iyov  אֵין אָדָם נִתְפָּס בִּשְׁעַת צַעֲרוֹ, Rashi- 

שאין אדם נתפס - להתחייב על שהוא מדבר קשה מחמת צער ויסורין דקאמר לא בדעת ידבר לא אמר לא ברשע ידבר אלא לא בדעת:

Rav Avremi Isenberg threw in the idea that he was pattur because as an onein, he was pattur min hamitzvos, and מורה לפני רבו is only because of מפני שיבה תקום or את ה' אלוקיך תירא; if he's pattur from the latter, he is pattur from the former.

Clever, but no cigar. First of all, the eisek with Nadav and Avihu was davka given over to Mishael and Eltzaphan and Klal Yisrael as a whole, so they did not have any ptur aninus. Second, pashtus Shmuel was a child and pattur min hamitzvos, too, and being pattur min hamitzvos did not protect him. Apparently, the chillul Hashem of moreh lifnei rabbo is a metziyus and the punishment is a metziyus too. As to whether the rebbi can be mochel- Reb Chaim Shmuelevitz here beginning on page 254 and especially on page 260 says there is no mechila. I don't know how he explains how Eli was mochel Shmuel, unless it's a combination of his being a kattan and mechilah. Rabbi Krasner in his Nachalas Shimon Shmuel I Siman 8 page 95 brings a Chasam Sofer; The Maharsha asks on Shmuel that he was a kattan and answers dinei shamayim are different. Everyone asks on the Maharsha that adderabba, missah bidei shamayim is not for an aveira done before the age of 20; so the Chasam Sofer says that the consequence of Moreh is not an onesh, it is what happens when you consume poison. (Like the Netziv says by machlokes.)

Chasam Sofer:

 ולפע"ד י"ל כך דמהרש"א הק' הא קטן הי' בן שני שני' ולא בר עונשי' הוא ותי' האי עונש בידי שמים הוא וצ"ע הא גם למעלה אין עונש לקטן אבל הכוונה כי המורה הלכה אינינו מטעם עונש אלא כאוכל סם המות ומת

See along those lines Reb Chaim Shmuelevitz in Shemini.