It is a sin-offering for the congregation— Whatever is human, is liable to error. Nations and churches are all fallible, and, therefore, an atonement for national sins of ignorance is provided. The offering is the same as for the priest, as, most likely, their sins would be the same. Note; If the people live in ignorance and sin, much is to be feared for their teachers.
Related Commentaries of Leviticus 4:21
Leviticus 4:21
21 And he shall carry forth the bullock without the camp, and burn him as he burned the first bullock: it is a sin offering for the congregation.