On the eighth day of the dedication of the Mishkan, Aharon, his sons, and the entire nation bring various korbanot (offerings) as commanded by Moshe. Aharon and Moshe bless the nation. G-d allows the Jewish People to sense His Presence after they complete the Mishkan. Aharon's sons, Nadav and Avihu, innovate an offering not commanded by G-d. A fire comes from before G-d and consumes them, stressing the need to perform the commandments only as Moshe directs. Moshe consoles Aharon, who grieves in silence. Moshe directs the kohanim as to their behavior during the mourning period, and warns them that they must not drink intoxicating beverages before serving in the Mishkan. The Torah lists the two characteristics of a kosher animal: It has split hooves, and it chews, regurgitates, and re-chews its food. The Torah specifies by name those non-kosher animals which have only one of these two signs. A kosher fish has fins and easily removable scales. All birds not included in the list of forbidden families are permitted. The Torah forbids all types of insects except for four species of locusts. Details are given of the purification process after coming in contact with ritually-impure species. Bnei Yisrael are commanded to be separate and holy like G-d.
Pans and Plans
"And the sons of Aaron, Nadav and Avihu, each man took his fire-pan." (10:1)
Nadav and Avihu made an error of judgment. They thought it was not only the Kohen Gadol who could bring the incense offering in the Holy of Holies, but that even they were permitted to do so.
They were great tzaddikim and no doubt pondered their conclusion before committing themselves to action.
The Midrash comments on the above verse that "each man" used his fire-pan; "each man" by himself, without seeking advice one from the other. The implication here is that if they had taken advice one from the other, if they had talked it over before they acted, that they would not have erred.
But why should they have arrived at a different conclusion. Seeing as they both did the same thing they both brought the "strange fire" it must be that they both were of the same opinion, that a non-Kohen Gadol was permitted to offer the incense. So even if they had consulted with each other, wouldn't they have still come to the same conclusion?
Such is the power of counsel. That even though two people may share an identical opinion, through discussion and mutual counsel they can arrive at the truth , which may be 180 degrees removed from what they both previously believed.
Source: Chidushei HaLev