Numbers 16:10

And he hath brought thee near [to him]
To be in his courts, to watch in his house, and wait on his priests, for which an ample provision was made by tithes. Korah is there personally addressed:

and all thy brethren, the sons of Levi, with thee;
the whole tribe of them, excepting Aaron and his family, who were advanced to be priests:

and seek ye the priesthood also?
the high priesthood, as the Targums of Onkelos and Jonathan; this opens the true cause of their discontent and rebellion; they could not be satisfied with being the ministers of the priests, but wanted to be priests themselves, and Korah perhaps to be high priest.