פּירוש אויף במדבר 8:8

ולקחו פר בן בקר AND LET THEM TAKE A YOUNG BULLOCK, — and this was to be a burnt offering, as it is said, (v. 12) “and thou shalt offer the one [as a sin offering] and the other as a burnt offering”, and it (a bullock) was the communal offering prescribed (Numbers 15:24) in case of idol worship committed by the community (here the firstborn are regarded as a community).

ולקחו פר בן בקר, “then let them take a young bullock, etc,” this was to serve as a consecration rite for the services they would perform henceforth. An alternate interpretation: they have to take a young bullock seeing that the firstborn whom they replaced had served the golden calf at the instruction of others, at that time. We derive this from the line in Exodus 32,4: אלה אלוהיך ישראל, “these are your gods, Israel.” In other words: someone, the mixed multitude seduced the Israelites. We find in Numbers 15,24: “then it shall be, if it be done in error by the congregation, it having been hidden from their eyes, that all the congregation shall offer one young bullock for a burnt offering, etc,” The subject there is the person who had inadvertently committed the sin of idolatry

What does the Torah teach [by specifying] ‘a second’? Though it is written “and the second sheep…” (Bamidbar 28:4) regarding the Tamid offering, this was because it is [also] written “the first sheep.” However here it is not written “the first,” therefore the terminology of “a second” is not appropriate.

ופר שני AND ANOTHER BULLOCK [THOU SHALT TAKE TO BE A SIN OFFERING] — What is the force of the word שני, the second? (There is no corresponding word אחד at the beginning of the sentence!). But it is used to suggest a comparison between the two sacrifices: How is it in the case of the burnt offering? It is not permitted to be eaten (for it is entirely burnt on the altar)! So, too, is this sin-offering not permitted to be eaten (in spite of being a חטאת חיצונה which as a rule may be eaten; cf. Rashi on Leviticus 9:11). And in this fact (that the חטאת prescribed was not eaten) there is some support in the statement of Torath Cohanim just quoted for his (R. Moses the Preacher’s) view (that the עולה which is paired with it was that enjoined for idolatry committed by the community) (cf. Sifra, Vayikra Dibbura d'Chovah, Chapter 3 4). — I, however, say that it (the fact that this חטאת was not to be eaten) was an occasional (exceptional) decision (הוראת שעה) (contrary to the rule of a חטאת חיצונה, and not because it was intended as a חטאת לע"ז as asserted by R. Moses), for if his view were correct they would have had to offer a goat (as prescribed in Numbers 15:24 not a bullock) as a sin offering to expiate for idolatry together with a bullock for a burnt offering mentioned here.