Leviticus 4:14

and the sin which they have sinned be made known to them; the congregation shall offer a young bullock as a sin offering, and shall bring him before the tabernacle of ordinance.

When the sin will be disclosed This rule also applies to the High Priest: as long as he does not realize his sin, and as long as he is not informed, he does not bring the bullock sin-offering. The reason why this rule — When the sin becomes disclosed — is mentioned first here, regarding the Sanhedrin, is that the High Priest is likely to inform them of their error, whereas no one is likely to inform the High Priest; he himself must become aware of his error. The sin-offering of the Assembly is identical in all details to the sin-offering of the High Priest. Thus, the High Priest is equal in stature to all Israel.

WHEN THE SIN WHEREIN THEY HAVE SINNED IS KNOWN [THEN THE ASSEMBLY SHALL OFFER A YOUNG BULLOCK …]. It is self-understood that they cannot offer a sin-offering until they know that they have sinned. [So why does Scripture mention it?] But it is a linguistic expression of the [Hebrew] language to say, “and when it becomes known to them that they have sinned, they should bring their offering.” Therefore He did not mention it [in Verse 3] in the case of the anointed priest, because there was no need for it. It is possible that [the reason why the verse says, when their sin wherein they have sinned is known, is not merely as a linguistic expression but to indicate] that the assembly is not obliged to bring this sin-offering unless they have definite knowledge of their sin but not if it is merely a doubt, as in the case of the suspensive guilt-offering. (suspensive guilt-offering) is brought in case of doubt about one of those major sins for which the penalty if committed wilfully is excision, and a sin-offering if committed unintentionally. This offering is called a suspensive guilt-offering. An example of a case of a doubt which calls for such an offering is the following. Suppose a person has before him two pieces of fat, one of which is Scripturally-forbidden food, and the other is permitted to be eaten, and he eats one of the two [whilst the other is eaten by another person or lost]. A doubt then arises in his mind as to whether the piece he has eaten was the permitted or the forbidden food. In such a case he must bring an offering so as to effect atonement, and this is called a suspensive guilt-offering. If it is later established that he ate the forbidden fat, he must then bring a sin-offering (See Maimonides, “The Commandments,” Vol. I, pp. 79-80). The point Ramban makes thus is that the verse before us teaches that the sin-offering of the assembly can be brought only when it is definitely confirmed that it has sinned [unintentionally], unlike the suspensive guilt-offering of the individual which is brought in case of doubt. Our Rabbis have interpreted, 4:12; Horayoth 5a. [that the verse says, the sin … is known, to teach that] “if the court knew that they had given an [incorrect] decision [on one of two kinds of forbidden food, such as fat and blood, declaring that one of them may be eaten], but did not know which one it was that they permitted, [and the people had eaten both], I might think that the court is obligated to bring a sin-offering [as they usually are when they give an incorrect decision which the people followed]. Scripture therefore says, when ‘the’ sin wherein they have sinned is known — not when only the sinners are known.” This is not mentioned in the case [of the sin-offering] of the anointed priest, since He said there: If the anointed priest shall sin so as to bring guilt on the people, thus declaring [the law of the sin-offering of] the anointed priest to be like that of the public.