Chabad.org — English translation + Rashi
Torah Temimah points to Horayos 10a (unit 2; single primary locus per emergency Core plan).
E-Daf.com — Horayos 10a
HebrewBooks / Shas PDF
English: It was taught: “When a nasi sins” — might this be a decree [that he will sin]? The verse of the anointed kohen teaches: just as there it is when he sins, so here it is when he sins.
Conditional, not inevitable, sin of the nasi — the verse does not decree that a nasi must sin; it addresses the case if he does.
The opening “asher nasi yecheta” is not a prophetic decree that every nasi will sin. Comparison with the parallel language for the anointed kohen shows that both verses speak of the contingency “when/if he sins,” not of an inevitable outcome. The nasi remains free of predetermined guilt.