פּירוש אויף במדבר 16:2

Those called to the assembly, men of renown. It appears that men of bitter heart who loved excessive honor and authority gathered to Korach, thinking that he would give positions of authority to all of them. For this was the desire of all men of renown who said among themselves, Let us make a name for ourselves lest we be held in contempt (Genesis 11:4). And this is proven by their opening words, It is too much for you (Numbers 16:3). For they said it is proper that authority should rotate from one person to another, saying “It is too much for you” — meaning that for many days you have exercised authority over Israel, and it is fitting that you give the staff of leadership to others, for all the congregation are holy (Numbers 16:3).
The word all is superfluous, but what they were saying is this: It is known that a congregation consists of no fewer than 10 people, and in every congregation of Israel, all are holy. Each congregation in itself possesses holiness, for nothing sacred can be done with fewer than 10. In every congregation of 10, there is holiness, and among them is the Lord (Numbers 16:3). And you not only exalt yourselves over a congregation of 10, but you exalt yourselves over the entire assembly of the Lord, and this cannot be tolerated.
That is why he began with congregation and concluded with assembly, suggesting that even if you were exalting yourselves over a congregation of 10, we would have reason to complain against you, since every congregation possesses holiness. How much more reason do we have to complain about why you exalt yourselves over the entire assembly of the Lord, over all of them together.
And regarding what is written, and among them is the Lord — for wherever you find the greatness of the Holy One, blessed be He, there you find His humility (Megillah 31a). Behold, the Holy One, blessed be He, demonstrates humility to Israel and walks among them, that is to say, in their midst and not at their head, as if to say, “I am like a brother and companion to you, and I do not seek to go at the head as would be My right.” So how can you exalt yourselves over the assembly of the Lord?

קריאי מועד, the ones who had been referred to in Numbers 1,16 as קרואי העדה. They would be invited to preside over litigation on the days appointed for this (מועד).

ויקומו לפני משה ואנשים מבני ישראל חמשים ומאתים, all these who ganged up on Moses and Aaron were from Korach’s own tribe, i.e. Levites. This is the meaning of Moses saying to them: “רב לכם בני לוי, “enough for you Levites, etc.” (verse 7), as well as when he again addressed them as בני לוי in verse 8, i.e. stressing that the people he was speaking to were all Levites. Perhaps these Levites had been under the impression that their whole tribe had been meant to be priests and that Moses had highhandedly decided to bestow this honour only on his brother Aaron.