Chabad.org — English translation + Rashi
Torah Temimah points to Horayos 3b (unit 2; single primary locus per emergency Core plan).
E-Daf.com — Horayos 3b
HebrewBooks / Shas PDF
English: What is “the whole congregation”? Thus it means: if the entire Sanhedrin is present it is a [binding] ruling, and if not — it is not a ruling.
Full Sanhedrin required for hora’ah — only a complete Sanhedrin issues the binding erroneous ruling that obligates the communal bull.
A binding hora’ah that triggers the par he’elam davar of the congregation exists only when the entire Sanhedrin participates. If even one member is absent, the decision lacks the formal status of hora’ah and the communal offering is not incurred. Completeness of the court is indispensable.