Ibn Ezra on Leviticus 16:3

בפר בן בקר. אין פירושו שיביא הפר אל הקדש רק שיתן משלו בתחלה פר חטאת לכפר עליו ועל הכהנים ויש אומרים גם הלוים בעבור שמצאו ואת שם אהרן תכתוב על מטה לוי והוא רחוק רק הלוים יחשבו עם ישראל: WITH A YOUNG BULLOCK. Its meaning is not that Aaron should bring the bullock into the holy place¹⁴Herewith shall Aaron come into the holy place: with a young bullock might be taken to mean that Aaron should bring the bullock into the Holy of Holies. Hence I.E.’s comment. but rather that he first bring a bullock of his own¹⁵From his own property. for a sin offering to atone for himself and the kohanim. Others say also for the Levites,¹⁶The bullock also atones for the Levites. for they found, And thou shalt write Aaron’s name upon the rod of Levi (Num. 17:18).¹⁷We thus see that the Levites and the kohanim form one unit. However, this is farfetched. On the contrary, the Levites are considered among the Israelites.