The Rebbe says:
1. In this week’s Torah portion the Torah tells us about how Korach incited the people against Moshe Rabbeinu (Moses our teacher) and his brother Aharon Hakohen (Aaron the High priest). This comes after last week’s story of the Miraglim (the spies) who had their own agenda and reported to the Jewish assembly that the Land of Canaan was not for them, even though Hashem (G-d) had promised to take the Jewish people into the Land of Canaan.
The basic thrust of Korach’s argument was that if every single Jew is a part of one, “Holy Nation”, as Hashem calls us, why is there only one Kohen Gadol (Aharon)? Korach said, “Why do you exalt yourselves over the congregation of Hashem?”
What finally pushed Korach to fight publicly with Moshe Rabbeinu was when Moshe appointed his younger cousin Elizaphan to be the Prince (Nassi) of the tribe of Levi and not Korach.