מדרש על במדבר 15:27

2) "unwittingly": He brings it only for unwitting (transgression), but not for intentional (transgression). Now does this not follow by kal vachomer? (Why is the exclusion clause necessary?), viz.: If in respect to the grave sin of idolatry, (where one would expect that a sin-offering should be brought for intentional transgression to help expiate the sin), intentional sin was not likened to unwitting sin, (a sin-offering being brought for the latter [see Bamidbar 15:27] but not for the former), should it not follow that with lesser mitzvoth intentional sin should not be likened to unwitting sin, (and a sin-offering not be brought for the former? [Why, then, the exclusion clause?]) — But that is just the point! If (atonement) for the grave sin of intentional idolatry is delayed until Yom Kippur, (a sin-offering not being able to atone for it), would you put off (possible atonement for) intentional (transgression of) lesser mitzvoth until Yom Kippur? Let him bring a sin-offering and gain atonement immediately! It is, therefore, written (in respect to lesser mitzvoth): "if he sin unwittingly." He brings (a sin-offering) for unwitting sin but not for intentional sin.

3) — But, in that case, should it not follow by kal vachomer that (a sin-offering not be brought for intentional) idolatry? (Why the exclusion clause? [Bamidbar 15:27]), viz.: If (atonement for) intentional (transgression of) lesser mitzvoth is delayed until Yom Kippur, (not being susceptible of atonement with a sin-offering), should not (atonement for) intentional (transgression of) the grave sin of idolatry be delayed until Yom Kippur? — Not so — if we are lenient with the lesser mitzvoth, (no sin-offering being required before Yom Kippur), should we be lenient with the grave sin of idolatry? Rather, let a sin-offering be brought (for intentional violation), and "keep things in abeyance" for him until (the complete atonement of) Yom Kippur. Therefore "unwittingly" must be stated both in respect to (transgression of other) mitzvoth and in respect to idolatry.

4) — But why not go in this direction? The nassi brings a she-goat (for unwitting transgression of idolatry [see Bamidbar 15:27]), and he brings a categorical guilt-offering (see Vayikra 5:15), and the high-priest brings a she-goat for idolatry and he brings a categorical gift-offering. Just as the nassi brings (a sin-offering) for deed-unwittingness (alone, without an error in ruling), so, the high-priest! It is, therefore, written: "to the guilt of the people." The high-priest is being compared to the congregation. Just as the congregation brings (a sin-offering) only where (beth-din) erred (in the ruling), and they (the people) sinned unwittingly (on the basis of that ruling), so, the high-priest brings (a sin-offering) only in like circumstances.