Chabad.org — English translation + Rashi
Torah Temimah points to Horayos 10a (unit 3; single primary locus per emergency Core plan).
E-Daf.com — Horayos 10a
HebrewBooks / Shas PDF
English: A nasi who left his high office and afterward sinned — he is like a commoner, as it is written “when a nasi sins” — while he is nasi.
Status at time of sin — only one who holds the nasi office when he sins brings the nasi’s chatas.
If a nasi steps down or is removed from office and only afterward commits a shegagah, he brings the ordinary individual’s chatas, not the nasi’s goat. The verse’s language “when a nasi sins” requires that the office be held at the time of the transgression.