Charles Ellicott Commentary Numbers 16:7

"and put fire in them, and put incense upon them before Jehovah to-morrow: and it shall be that the man whom Jehovah doth choose, he [shall be] holy: ye take too much upon you, ye sons of Levi." — Numbers 16:7 (ASV)

Ye take too much upon you ... — Moses here adopts the language of Korah in Numbers 16:3. The meaning appears to be, as more fully explained in Numbers 16:9-10, that it should have sufficed Korah and the other Levites that they had been chosen from among their brothers to perform the lesser duties of the sanctuary.