Musar sobre Números 26:9

Another problem is that Rashi writes that the prince Elitzur ben Shedeyur and some of his asscociates of the tribe of Reuben, was one of these two hundred and fifty men! Rabbeynu Bachyah writes on this subject that even the princes who had offered the 12 offerings described in Parshat Nasso were part of the two hundred and fifty men. Our sages further point out that in one place these men were described as קריאי מועד, and in another place as נשיאי העדה. In Parshat Bamidbar 1,16, they are referred to as קרואי העדה, נשיאי מטות אבותם. We know from Numbers 26,9, that the term קריאי העדה is used by the Torah for people who had provoked Israel into rebellion against G–d. It is certainly mindboggling to think that people of such calibre who had witnessed all these miracles should forfeit their standing as holy people by joining such a self-seeking rebellion. When we think of someone like Nachshon ben Aminadav who had risked his life being the first to enter the sea before it had even split, it is quite inconceivable that he should have lowered himself to such a degree! On the contrary, we find that Nachshon's merit even helped his descendants long afterwards, since our sages say that it did not prove helpful anymore to Elimelech the husband of Naomi in the book of Ruth, since the latter emigrated from the land of Israel (Baba Batra 91a).

And (Sanhedrin 101a): "R. Chisda said: 'If one argues against his Rabbi, it is as if he would argue against the Shechinah, viz. (Numbers 26:9) ["who strove against Moses and Aaron with the congregation of Korach] when they strove against the L-rd."' And R. Chamma b. Chanina said: "If one quarrels with his Rabbi it is as if he would quarrel with the Shechinah, viz. (Numbers 20:13): "They are the waters of Merivah (contention), whereby the children of Israel strove with the L-rd" [in striving with Moses].'" And, along the same lines: "R. Chaina b. Pappa said: 'If one rails against his Rabbi, it is as if he would rail against the Shechinah, etc.' … R. Avihu said: 'If one arraigns his Rabbi, it is as if he would arraign the Shechinah, etc.'" And the four levels that the Gemara mentions below are meant to apprise us that even thinking alone [against one's Rabbi] is also a great issur.