וַיֹּ֣אמֶר מֹשֶׁ֣ה אֶֽל־אַהֲרֹ֡ן וּלְאֶלְעָזָר֩ וּלְאִֽיתָמָ֨ר ׀ בָּנָ֜יו רָֽאשֵׁיכֶ֥ם אַל־תִּפְרָ֣עוּ ׀ וּבִגְדֵיכֶ֤ם לֹֽא־תִפְרֹ֙מוּ֙ וְלֹ֣א תָמֻ֔תוּ וְעַ֥ל כָּל־הָעֵדָ֖ה יִקְצֹ֑ף וַאֲחֵיכֶם֙ כָּל־בֵּ֣ית יִשְׂרָאֵ֔ל יִבְכּוּ֙ אֶת־הַשְּׂרֵפָ֔ה אֲשֶׁ֖ר שָׂרַ֥ף יְהוָֽה׃
Mose sprach dann zu Aaron und zu seinen Söhnen Elasar und Itamar: Eure Häupter sollt ihr nicht kahl machen und eure Kleider nicht zerreißen, dass ihr nicht sterbet und [Gott] über die ganze Gemeinde zürne. Aber eure Brüder, das ganze Haus Israel, dürfen die beweinen, welche der Herr verbrannt hat.
Zohar
The firstborn Nadab stands on his own merits and Abihu rests on his own, that each one are considered in the eyes (of the Torah) as both Elazar and Itamar (combined). But Nadab and Abihu by themselves are each considered equal to the seventy members of the Sanhedrin who served before Moses. For this reason, their deaths atoned for Yisrael. Therefore, it is written, "But let your brethren, the whole house of Yisrael bewail the burning" (Vayikra 10:6). Rabbi Shimon said: "Nadab the firstborn," meaning he is the one that all acclaim and praise are his. How much more so with Nadab and Abihu (together), because these two have no equal among all Yisrael.