Chabad.org — English translation + Rashi
Torah Temimah points to Horayos 10a (unit 5; single primary locus per emergency Core plan).
E-Daf.com — Horayos 10a
HebrewBooks / Shas PDF
English: If he sinned before he was appointed and afterward was appointed — he is like a commoner.
Prior sins do not trigger nasi chatas — sins committed before elevation to nasi are atoned as an ordinary individual’s.
A person who sinned while still a private individual and was later appointed nasi does not bring the nasi’s chatas for those earlier transgressions. The status that governs the offering is the status at the time of the sin, not the status at the time of discovery or atonement.