Levítico 8:14 Midrash: Sifra

12) (Vayikra 8:14): ("And he presented the bullock of the sin-offering, and Aaron and his sons placed their hands on the head of the bullock of the sin-offering.") "And he presented the bullock of the sin-offering": In the beginning, it was not called "the bullock of the sin-offering," viz. (Shemoth 29:1): "And this is the thing that you shall do to them to sanctify them to minister unto Me: Take one young bullock and rams, etc." In its specific accounting it is called "the bullock of the sin-offering," viz. (Shemoth 29:14): "And the flesh of the bullock and its hide and its waste you shall burn in a fire outside the camp — it is a sin-offering." We do not know whether this refers to the sin-offering of Aaron and his sons or to the communal sin-offering. "Take Aaron and his sons with him … and the bullock of the sin-offering" (Vayikra 8:2) tells us that it is the sin-offering of Aaron and his sons and not the communal sin-offering.

13) "and Aaron and his sons placed their hands on the head of the bullock of the sin-offering.": We find that Aaron and his sons perform semichah (the placing of the hands) on all of their offerings. But because they do so because they are their offerings, the offerings of partners are compared to their offerings, viz.: Just as their offerings require semichah for each of the participants, so the offerings of partners require semichah for each partner.