What was Moshe referring to when he said to Aharon "Hu Asher Diber Hashem 'bi'Kerovai Ekadesh' "?
Rashi (citing Zevachim, 115b): He was referring to Hashem's statement to Moshe (in Sh'mos 20:43) "Veno'adti Shamah li'Venei Yisrael, Venikdash bi'Chevodi" - as if it had written 'Venikdash bi'Mechubadai' (and it [the Mishkan] will be honored by (the death of) My honored ones.' 1
Ramban and Moshav Zekenim #1: It is not referring to any prior statement of Hashem, but is rather a direct reference to the death of Nadav and Avihu, as if to say 'This is what Hashem decreed, saying (in His heart) 2 that He will be sanctified via those who are close to Him - that they should not breach His Kedushah, and that He will be honored via all the people - that they should behave respectfully in His Mishkan.
Rashbam: When Aharon's sons died and he wanted to leave the Avodah and mourn for them, Moshe informed him not to mourn, not to cry and not to desecrate the Avodah by leaving it, because Hashem had told him that He wished to be sanctified by the Kohanim Gedolim 3 not leaving the Avodah - by not mourning, but continuing to serve as if nothing had happened. 4
Moshav Zekenim #2: Hashem had said "ve'Gam ha'Kohanim ha'Nigashim el Hashem [Yiskadashu Pen Yifrotz bahem Hashem" - Yisro Sh'mos, 19:22, 5 even the conditional curse of a Chacham materializes (even if the condition is not fulfilled), how much more so that of Hashem.
Moshe was now informing Aharon that he knew that something like this would happen, only he thought that the victim would be either himself or Aharon. Now he knew however, that Nadav and Avihu were greater than they were (Rashi). See Rashbam's objection to this explanation. Targum Yonasan however, explains that Moshe was only relating the warning that Hashem had issued on Sinai, that if the Kohanim are not careful when performing the Avodah, they will be burned by means of a fire that comes from Hashem.
See Koheles, 1:16. This is similar to Yehoshua, 5:4 and Bereishis 24:51.
Because during the Milu'im, Aharon's sons were considered like Kohanim Gedolim.
As the Pasuk specifically states in 21:10-12; as that Parshah preceded this one - 'Ein Mukdam u'Me'uchar ba'Torah (Rashbam).
Even though that Pasuk actually referred to ascending Har Sinai
If Nadav and Avihu were Chayav Misah already at Har Snai, why did Hashem choose the current moment to kill them?
Oznayim la'Torah: In order to punish them in the presence of all of Yisrael ? so that the (Hashem and the) Mishkan should be sanctified in public. 1
Why is Hashem's esteem enhanced when He carries out Din on Tzadikim?
Rashi: Because people will then say that if Hashem performs judgment on Tzadikim, how much more so will He do so on Resha'im. 1 And so the Pasuk writes in Tehilim, 68:36 "Nora Elokim mi'Mikdashecha" - as if it had written 'mi'Mekudashecha' (Hashem is awesome when He performs Din with His holy ones).
Ramban: And they will know that He dwells among them. Da'as Zekenim - they will guard themselves from sin and fear Him.
What is "al-P'nei Kol ha'Am Ekaved" referring to?
Ramban: Refer to 10:3:1:2.
Rashbam: It refers to when they see that Aharon's sons died, yet he refrains from mourning and continues with his Creator's Avodah. Refer to 10:3:1:3.
What are the connotations of ?Vayidom Aharon??
Ramban #1, Moshav Zekenim: He stopped sobbing loudly.
Ramban #2: His eyes stopped shedding tears. 3
Rashbam: He refrained from crying and from mourning. 4
Seforno: He was comforted by the Kidush Hashem that resulted from his sons' death.
Moshav Zekenim: Similarly the Navi states in Yehoshua 10:13 "va'Yidom ha'Shemesh" - when a Tzadik dies, even the sun stops singing Shirah.
But accepted the decree with love (Rashi, 11:2).
As in Eichah, 2:18 [Ramban]).
Like we find by Yechezkel, 24:16 & 17.
If Aharon?s remaining silent was considered praiseworthy, what reward did he receive?
Rashi #1: The Parshah of Shesuyei Yayin (in Pasuk 8) was said to Aharon alone. 1
See Sifsei Chachamim, who reconciles this with Rashi in Vayikra, 1:1.