Komentaryong Sumisipi para sa 2 Cronica 35:11

ושחט את בן הבקר, ”he will slaughter the bull, etc.” We have a tradition (Sifra Vayikra 4,2) that slaughtering the sacrificial animal by a non priest (layman) was in order. This is the reason the Torah wrote the word: “he will slaughter,” without being precise as to who will perform this procedure. In other words, “anyone.” Whenever the Torah defines procedures in the plural, such as “they will sprinkle,” “they will burn, etc.,” it invariably refers to priests who have been mentioned previously in that context. If such a plural is followed by a singular such as in verse 6, והפשיט את העולה, “he will skin the burnt-offering;” this means that whoever had performed the last procedure will continue with the present procedure. [The author has to show that the use of the singular does not always mean that a non priest could perform such a procedure. Ed]. The reason that the Torah uses the word בן בקר all of a sudden instead of the word פר used to describe a bull previously, is that the age of the animal, i.e. not over 2 years old is meant here. The term עגל, calf, is used for animals up to one year old, whereas the term פר indicates that the animal is in its third year. Whenever the Torah speaks of כבש or כבשים, one year old sheep (male) are meant, whereas the two year old male sheep are called איל.
Rabbi Meir (in Rosh Hashanah 10) claimed that when the Torah speaks of עגל without adding that it is one year old, what is meant is a one-year old calf. When the Torah speaks of בן בקר a two year old bull is meant. When the Torah speaks of פר without specifying further, a three year old bull is meant.
In Torat Kohanim (Sifra Vayikra 3,6) we are taught that the reason an עגל is a one year old calf is that the Torah speaks in Leviticus 9,3 of “a one year old calf and a one year old sheep.” The reason we know that the term בן בקר applies to a two year old bull is also because the Torah writes in 9,2 עגל בן בקר לחטאת ואיל לעולה תמימים, “a two year old male calf as sin-offering, and a ram as burnt-offering, they are to be flawless.” Just as the calf mentioned there is two years old so the ram is two years old. Just as both have to be flawless, so both have to be of the same age (approx.). Thus far Torat Kohanim. However, speaking of male goats, when it is referred to as שעיר without adjective it is under one year old. Once it is a year old it is referred to as שעיר עזים.

And their brethren the Levites were appointed for the entire service of the Tabernacle of the House of God for gate sentries and to flay [the sacrificial animals], as is written further: (II Chron. 35: 11): “...and the Levites were flaying.”