Albert Barnes Commentary Numbers 17:3

"And thou shalt write Aaron`s name upon the rod of Levi; for there shall be one rod for each head of their fathers` houses." — Numbers 17:3 (ASV)

Thou shalt write Aaron’s name upon the rod of Levi - The Levites had taken part in the late outbreak. It was therefore necessary to vindicate the supremacy of the house of Aaron over them; and accordingly his name was written on the rod of Levi, although being the son of Kohath, the second son of Levi (Exodus 6:16 and following), he would not be the natural head of the tribe.