In Parshat Shimini, Nadav and Avihu, the ill-fated sons of Aharon, bring unlicensed Ketoret to Hashem and are immediately consumed and killed by fire. The Midrash in Torat Kohanim comments that Nadav and Avihu’s actions disrespected their father, Aharon, and that they should have brought their plans to Moshe in the first place. Furthermore, says the Midrash, they acted independently of each other, as the Pasuk states, “Vayikchu Bnei Aharon Nadav Vaavihu Ish Machtato,” implying that they brought their Ketoret separately. For this, they certainly deserved to be punished.
The Brisker Rav zt”l finds this Midrash puzzling. Why would the brothers have been punished any more or less severely had they acted as a unit? He explains that the Midrash is actually trying to teach a lesson about human nature. Usually, when a group has in mind to perform a forbidden action, members of the group consult with each other first and hopefully decide collectively to not follow through with their plans. Unfortunately, Nadav and Avihu acted individually, and when one person alone decides to do an illegal act, his self-interest and Yetzer Hara blind his conscience from convincing him to do the right thing. Had they conferred with each other at the start, Nadav and Avihu might have dissuaded each other from bringing a Ketoret Zarah, which would have allowed them to serve as Kohanim for many years to come.
The story of Nadav and Avihu emphasizes the important fact that there are severe consequences for unwarranted actions. Even more so, it clearly demonstrates the need for collective decisions in all sorts of situations, which hopefully can avoid foolish actions.
-Adapted from a Dvar Torah in Talelei Orot