וְאִם־נֶ֧פֶשׁ אַחַ֛ת תֶּחֱטָ֥א בִשְׁגָגָ֖ה מֵעַ֣ם הָאָ֑רֶץ בַּ֠עֲשֹׂתָהּ אַחַ֨ת מִמִּצְוֺ֧ת יְהוָ֛ה אֲשֶׁ֥ר לֹא־תֵעָשֶׂ֖ינָה וְאָשֵֽׁם׃
若民間有一個人無意中犯了罪，觸犯了永恆者所吩咐不可做的任何一條誡命，因而有了罪咎：
Ibn Ezra
an ordinary person denotes all Israelites, all ordinary kohanim, and all Levites.
Sforno
ואם נפש אחת תחטא בשגגה מעם הארץ, if an ordinary citizen had committed an inadvertent sin, a likely event; here the Torah describes the sin as חטא, whereas when speaking of the King it describes it as אשם, in order to warn him at the same time to confess and do teshuvah before offering his sin offering. In both instances, as well as in all sacrifices described as asham, part of the sacrificial meat is eaten by the priests. The eating of those parts of the sacrifice by the priests is an essential ingredient in the atonement process for the guilty parties.
Or HaChaim
ואם נפש אחת תחטא, And if anyone of the common people sin through error, etc. The letter ו at the beginning of the word ואם connects this paragraph to the rules established in the previous paragraphs concerning the details of the procedures.