Rabbi Yirmeya ben Elazar said: In four places,49Leviticus 10:1, 16:1; Numbers 3:4, 26:61. it mentions the death of Aaron’s sons, and in all of them it mentions their sin. Why to that extent? It is to inform you that they had committed only this sin alone. Rabbi Elazar HaModa’i said: Come and see how difficult the death of Aaron’s sons was before the Holy One blessed be He, as every place that it mentions their death, it mentions their sin.
Why to that extent? To prevent the possibility of slander, so that people should not say: ‘They clandestinely committed corrupt actions and that was the reason they died.’ “Nadav and Avihu died before the Lord.” Rabbi Yoḥanan said: Did they die before the Lord?
It teaches that it is difficult before the Holy One blessed be He when the children of the righteous die during their fathers’ lifetimes. “When they offered alien fire before the Lord,” Rabbi Yoḥanan of Yafo raised a question before Rabbi Pinḥas bar Ḥama in the name of Rabbi Simon: Here [in this verse] it says “before the Lord,” “before the Lord,” twice, but elsewhere50The same midrash appears in Midrash Rabba Acharei Mot 20:10 and was apparently copied over to here without correcting the references.
In the context of Bamidbar it should say "Elsewhere [in this verse] it says “before the Lord,” “before the Lord,” twice, but here is says…" it says: “In the presence of Aaron their father,” once. This teaches that it was twice as difficult before the Holy One blessed be He as it was for their father.