Commentary for Leviticus 4:8

ואת כל חלב פר [AND HE SHALL TAKE UP …] ALL THE FAT OF THE BULLOCK — It ought to have said “its fat” (since the פר has just been mentioned); why does it state expressly “the fat of a bullock [of a sin-offering]” (i.e. any bullock brought as a sin-offering)? In order to include also the bullock of the Day of Atonement in respect to the burning of the kidneys, the fat portions and the lobe (Sifra, Vayikra Dibbura d'Chovah, Chapter 4 1).

The bullock of Yom Kippur. Re”m writes: They taught the same in regard to “He shall spill all the bullock’s blood” — It should have stated [“its blood,”] etc. Rather, [it comes] to include the bullock of Yom Kippur for spilling [the blood]. Rashi, however, only brings what they derived from the verse: “And all the fat of the bullock,” but I do not know why. It appears that it is because it is a disagreement between Rabbi Akiva and Rabbi Yishmael, as cited in the Yalkut on this Parshah (pg. 157, see there). (Minchas Yehudah). Rashi did not bring this because in Zevachim (25a) they derived another matter from this verse — that the one who slaughters needs to receive all the blood of the bullock (Gur Aryeh).

החטאת — [THE FAT OF THE BULLOCK OF] THE SIN OFFERING (implying, the fat of the bullock because it is a sin-offering) consequently serves to include the goats brought as a sin-offering for idolatry (Numbers 15:24) in respect to the burning of the kidneys, the fat portions and the lobe of the liver (Sifra, Vayikra Dibbura d'Chovah, Chapter 4 1; cf. Note on the previous passage).