- How many judges are required for various Torah laws
The opening Mishnah states: דיני ממונות בשלשה – monetary cases are judged by a court of three judges. גזילות וחבלות בשלשה – Cases of robbery and personal injury are judged by a court of three judges. The Mishnah proceeds to list numerous cases which are judged by three judges, some of which are subject to a machlokes, such as מוציא שם רע, malkus, or instituting a leap year. Chalitzah and מיאון are performed before a Beis Din of three, and produce is appraised for redemption (e.g., from maaser sheni or hekdesh) by three judges. The Mishnah continues: דיני נפשות בעשרים ושלשה – capital cases are judged by a Beis Din of twenty-three judges. The same applies to cases of stoning an animal for having relations with or killing a person. The Mishnah then lists the cases that require the full Sanhedrin of seventy-one judges, such as judging a shevet for avodah zarah, a false נביא, or a Kohen Gadol. Their consent is needed before going out to an optional war, and additions to the city of Yerushalayim or the עזרות of the Beis Hamikdash must be made by the Beis Din of seventy-one judges.
- Sources for the number of judges in סנהדרין גדולה and courts for דיני נפשות
The Mishnah provides the source for the number of judges in the סנהדרין גדולה. The passuk says: אספה לי שבעים איש מזקני ישראל – Gather for Me seventy men from the elders of Yisroel, and Moshe was over them, totaling seventy-one. Rebbe Yehudah says the Sanhedrin was seventy judges. A “lesser” sanhedrin requires twenty-three judges, based on the pesukim: "ושפטו העדה" "והצילו העדה" – and the congregation shall judge…and the congregation shall save. This requires enough judges to have עדה שופטת ועדה מצלת – a congregation (of ten) which “judges” to convict the accused, and a congregation which “saves” him through acquittal, thus requiring twenty judges. The passuk says not to follow the majority "לרעות" – for harm, i.e., to convict, which implies to follow the majority לטובה – for good, i.e., to acquit. Why, then, does another passuk need to say to follow the majority? It teaches: לא כהטייתך לטובה הטייתך לרעה – your “leaning” for good is not like your “leaning” for harm: we lean to follow a single-vote majority to acquit, but require a two-vote majority to convict. Finally, a Beis Din cannot have an equal number of judges (to allow for an acquittal of one), thus totaling twenty-three.
- First opinion: מדאורייתא, three מומחין are required, but this requirement was waived for loans
The Gemara asks why the Mishnah separately lists “דיני ממונות” and “גזילות וחבלות”, which themselves are monetary laws, and Rebbe Abahu explains that the Mishnah is defining which monetary laws are intended, to the exclusion of הודאות והלואות – cases of admissions and loans (i.e., disputes involving loans). Since Rebbe Abahu rules elsewhere that three judges are required for all monetary cases, the Gemara explains that the Mishnah means to exclude הלואות from requiring מומחין – ordained judges (with סמיכה). Since he requires three judges for הלואות, and the same passuk requiring three judges also requires מומחין, the Gemara concludes that Biblically, Rebbe Abahu would require three מומחין for הלואות, but the Sages waived the מומחין requirement to more easily facilitate loans. On the next Daf, Rava concludes by explaining the laws like Rebbe Abahu, but reads the Mishnah as two cases: (1) “monetary laws,” meaning loans, requiring three judges but not מומחין, and (2) גזילות וחבלות, requiring three מומחין.