Ibn Ezra on Leviticus 4:14

ונודעה החטאת. וכן משפט הכהן הגדול ואם איננו נזכר כי אם לא הודע אליו חטאתו לא יקריב פר החטאת. ויש אומרים כי בכל שנה יקריב כן שמא חטא. והזכיר עם כל עדת ישראל ונודעה החטאת שהכהן יתכן שיודיעם ואין מי שיודיע לכהן רק מעצמו. וחטאת הקהל כחטאת הכהן הגדול בכל משפטיה. והנה הכהן הגדול שקול כנגד כל ישראל: WHEN THE SIN WHEREIN THEY HAVE SINNED IS KNOWN. The same law,²¹A person shall bring a sin offering only after learning that he has sinned. The same law applies to the kohen gadol. even though it is not mentioned,²²Scripture doesn’t state, “when their sin is known” in the law dealing with the kohen gadol. applies to the kohen gadol, for if the sin not be known to the kohen gadol, then he does not bring a sin offering. Others say that the kohen gadol shall bring this sacrifice²³A sin offering. every year because he may have sinned.²⁴Hence Scripture does not state “when the sin wherein he sinned is known” with regard to the kohen gadol. Scripture mentions the sin…is known with regard to the whole congregation of Israel, for it is possible that the kohen will inform them. However, there is no one to inform the kohen; he informs himself.²⁵The kohen gadol realizes by himself that he has sinned. The sin offering of the congregation is the same as that of the kohen gadol in all details. The kohen gadol is thus equivalent to all of Israel.²⁶Hence their sacrifices are equal.