Leviticus 10:2
1 Then Aaron’s sons, Nadab and Abihu, each took his fire pan and put fire in it, set incense on it, and presented strange fire before the Lord, which he had not commanded them to do. 2 So fire went out from the presence of the Lord and consumed them so that they died before the Lord. 3 Moses then said to Aaron, “This is what the Lord spoke: ‘Among the ones close to me I will show myself holy, and in the presence of all the people I will be honored.’” So Aaron kept silent. 4 Moses then called to Mishael and Elzaphan, the sons of Uzziel, Aaron’s uncle, and said to them, “Come near, carry your brothers from the front of the sanctuary to a place outside the camp.”
Leviticus Rabbah 12
AggadahThis divine statement was made to Moses on Mount Sinai, but he himself did not understand it until the incident of Nadab and Abihu occurred. When, just before that incident, God was made present to the people (Leviticus 9:24)] Moses said to God: 'Master of the Universe, who is there more beloved [to You] than me and my brother Aaron? [Are we not the ones] by whom this house will [now] be sanctified?' After Aaron's two sons entered to sacrifice and came out burnt, Moses [now understood and] said to Aaron, 'Aaron my brother, your sons died for the sake of sanctifying God's name. That is what He meant by 'I will be made holy by those who are near [and dear] to me [that is, Nadab and Abihu] and then, as a result before all the people I will be honored' [Leviticus 10:3]
Notes and References
"... According to one version Moses says that Nadab and Abihu have greater merit than either he or Aaron, since they were chosen to consecrate the Tabernacle by their death. According to the other version Moses declares that Nadab and Abihu died for the sanctification of God's name, thus giving Aaron to understand his sons' proximity to God. Sifra also attributes two noble motives to Nadab and Abihu: 1) They concluded that fire was necessary because the divine presence, had been withheld from Israel. God said to them: 'I shall honor you more than you have honored Me; you brought Me impure fire, but I will burn you with pure fire' 2) Upon beholding the fire of divine approval immediately preceding their action (Leviticus 9:23—24), they joyfully arose 'to add love to love,' Other traditions attested in PRK and Leviticus Rabbah insist that Nadab and Abihu were guilty of only one (unspecified) sin, to which Scripture consistently alludes; consequently no one may presume any other transgression on their part. Despite gazing too boldly at the divine presence, they nonetheless derived spiritual nourishment from it. Their death was as grievous to God as it was to their father Aaron. Finally, they are considered to have suffered 40 the death of the righteous ..."
Kirschner, Robert The Rabbinic and Philonic Exegeses of the Nadab and Abihu Incident (Lev. 10:1-6) (pp. 375-393) The Jewish Quarterly Review. Vol. 73, No. 4, 1983