Nadav and Avihu, sons of Aharon, brought "foreign fire" before Hashem. Fire came out from "before Hashem," consuming them, so that they died "before Hashem." Later, Hashem commanded their cousins to remove them "from the face of the holy place" (Vayikra 10: 1-4).

Where did these tragic events take place, and what does this teach us about the underlying elements of the episode that transpired? Rav Acha and Rav Z’eira (Vayikra Rabba 20:5), who compared the matter to Titus’ entry into the Holy of Holies, apparently understood that Nadav and Avihu were killed there. Another indication is that the commandment in Acharei Mot about not entering the Holy of Holies was introduced with the words "after Aharon’s two sons died, as they approached before Hashem and they died" (ibid. 16:1).

On the other hand, it is logical that Nadav and Avihu were in the kodesh (the Holy) at the time. After all, they were offering incense, and the gold altar upon which this was done was in the kodesh. Rav Yishmael felt that this view was implied by the description "before Hashem." Tosafot (Eruvin 63a) and the Ibn Ezra posit that the tragedy transpired in the azara (courtyard) of the Mishkan, where the altar for animals stood. This connects the fire that killed them to the fire that had previously come from the Heavens to consume the offerings on that altar (Vayikra 9:24).

The Meshech Chochma develops this idea in a brilliant manner that explains the next section as well. The following p’sukim tell of Moshe’s complaints against Aharon’s remaining sons for not eating a certain korban that day. The pasuk tells us that the se’ir hachatat sacrifice was burned. Moshe said that there was no reason to have done that because the blood had not been brought into the kodesh. Much has been written to try to uncover the exact disagreement between Moshe and Elazar and Itamar, "Aharon’s remaining sons." The simple meaning of the words implies that they thought that the korban was an inner korban and was thus burned, whereas Moshe thought that it was an external korban. However, it should have been a clear fact which type of korban it was, so what was the argument? Also, what is the connection between this question and the story of Nadav and Avihu, which would justify their being called "the remaining sons," implying that they were barely spared from their brothers’ fate?

The Meshech Chochma explains that Nadav and Avihu believed that at this time of spiritual elevation, everything was "upped a notch" spiritually. The outer altar should be treated like the inner one and could be used for incense. Similarly, Elazar and Itamar felt that the korban that was brought on the outer altar should be treated like those brought on the inner. As the two mistakes were similar to each other, it was only because of Aharon’s merit that the remaining sons were spared despite their mistake (see Yoma 87a).