וְ֠נָתְנוּ בְּנֵ֨י אַהֲרֹ֧ן הַכֹּהֵ֛ן אֵ֖שׁ עַל־הַמִּזְבֵּ֑חַ וְעָרְכ֥וּ עֵצִ֖ים עַל־הָאֵֽשׁ׃
און די קינדער פֿון אַהרן דעם כֹּהן זאָלן אַרױפֿטאָן פֿײַער אױפֿן מזבח, און אָנלײגן האָלץ אױפֿן פֿײַער.
Rashbam
ויקחו בני אהרן נדב ואביהוא, before the fire had emanated from the Holy of Holies they each took his own pan planning to offer incense on the golden altar, seeing that this offering precedes (timewise) the disposal of not totally burned leftovers from the previous day’s sacrificial meat. They placed “alien” fire on these pans, something which had not been commanded by Moses to be done on this day. Even though on ordinary days the rule of “the sons of Aaron will place in these pans fire on the altar” (Leviticus 1,7) was in effect, this rule did not apply to the day of inauguration, and Moses had not wanted any man made fire to be introduced into the Tabernacle. This was because he expected heavenly fire to manifest itself so that the addition of man made fire would have completely ruined the impact of the miracle. On this day the name of G’d would be glorified by all the people becoming aware of Divine approval of their offerings, by G’d accepting same by means of heavenly fire We find a parallel to this in Kings I 18,25 when the prophet Elijah on Mount Carmel ordered the priests not to put any fire on the altar.
Da'at Zekenim
אחרי מות, “after the death;” when we read in Kohelet 9,2: כטוב כחוטא, “as is the good man so is the sinner,” this is a reference to the two sons of Aaron who died only on account of having arrogated to themselves the right to preempt their elders Moses and Aaron in issuing a religious ruling. This is the meaning of the Talmud, tractate Yuma, folio 53, where Rabbi Eliezer explained the word חוטא as referring to their having done so. What precisely was the “new” ruling that they revealed? They interpreted the line: ונתנו בני אהרן הכהן אש על המזבח, ”the sons of Aaron the priest placed fire (man made) on the altar;” (in addition to the fire that came down from the heaven). (Leviticus 1,7) Their sin was basically the same as that of Korach and his congregation, and that is why both were burned to death by heavenly fire. (Compare Tanchuma on our portion, section 1) Rabbi Acha son of Ze-ira adds (in the Tanchuma) that this is also the meaning of Job 37,1: אף לזאת יחרד לבי ויתר ממקומו, “also on account of this my heart quakes and leaps from its place;” he compares what happened to the staff of Aaron when it was placed inside the Sanctuary which sprouted almonds, whereas his sons when they entered the Sanctuary were burned to death. (Numbers 17,23) He also contrasts the fact that the Roman general Titus dared to enter the Holy of Holies, and he left it unharmed although surely he was less qualified to have entered such sacred grounds. He had entered in order to blaspheme, whereas the sons of Aaron had entered in order to offer incense to the Lord. (Tanchuma section 4 on our portion) [No wonder at the reaction of Job when he reflected on this phenomenon. Ed.] This phenomenon is also the subject of Psalms 78,63: בחורי אכלו אש ובתולותיו לא הוללו, “Fire consumed their young men and their maidens remained unwed.” The psalmist explains the reason that the sons of Aaron had to die as being that they had failed to get married. They had described themselves as so superior that no one was good enough to become their wives. They overestimated the value of having been born into such prominent families as their father and uncle. The result of their haughtiness was that they died without leaving behind any children. (Tanchuma section 6) In other words, no one remembered them.
Kli Yakar
Therefore, the obligation of explanation falls upon me to advocate for all these opinions, and to say that all of them found support from this verse because they found it difficult [to understand]: Isn’t it already stated And the sons of Aaron the priest shall put fire, etc. (Leviticus 1:7) that there is a commandment to bring [fire] from ordinary [sources], so how can it say which He had not commanded them? And one cannot say, as Abarbanel says, that they should have taken the fire for the incense from the altar of burnt offering, because that commandment was [given] after the death of Aaron’s sons, and there it states And he shall take a censer full of burning coals of fire from before the Lord, etc. (Leviticus 16:12). Therefore, it is appropriate to interpret this strange fire as referring to strangeness and alluding to other matters that are hinted at in the [phrase] strange fire.