Chapter one of tractate Sanhedrin concludes with Mishnah six, and in it we will examine the source of the numbers upon which the courts are built - twenty-three and seventy-one. We will preface with a note: The word "Sanhedrin" is a Greek word that was absorbed into rabbinic language, and its meaning is a court or a council of sages. There are two types: the Great Sanhedrin and the Lesser Sanhedrin.
The Court System:
The Great Sanhedrin - Consisting of seventy-one judges, and there is only one. Its seat was in the Chamber of Hewn Stone, the chamber of hewn stones in the Temple complex.
Two Sanhedrins of twenty-three - Intermediate courts to which the city courts turned before elevating their questions to the Great Sanhedrin. One, the lower of the two, sat at the entrance to the Temple Mount, and the second, the higher one, at the entrance to the Courtyard.
The Lesser Sanhedrin - Consisting of twenty-three judges, in each and every city, and its primary concern was capital cases.
The Number Seventy-One:
We learned in the Mishnah: "Sanhedrei gedolah hayetah shel shivim ve'echad, uktanah shel esrim vesheloshah" - The Great Sanhedrin consisted of seventy-one, and the lesser of twenty-three. And from where do we know that the Great Sanhedrin is of seventy-one? From the verse in the Torah portion of Beha'aloscha, in which the Almighty says to Moshe Rabbeinu: "Esefah li shivim ish miziknei Yisrael" - Gather for Me seventy men from the elders of Israel. That is seventy, "uMoshe al gabeihen" - and Moshe sits at their head, "harei shivim ve'echad" - thus making seventy-one.
Rabbi Yehudah disagrees and says seventy, meaning that Moshe Rabbeinu is not counted as part of the Sanhedrin, but rather only the seventy elders. And even though with an even number the court is balanced, Rabbi Yehudah maintains that this is what is explicitly stated in the verse. However, the halachah follows the first Tanna: seventy-one, including the Nasi. This is the Great Sanhedrin.
The Number Twenty-Three:
The source of this number is more complex. One verse says "The congregation shall judge", and another verse says "The congregation shall save". From here we see that two separate congregations are required: a judging congregation, which has the power to condemn, and a saving congregation, whose role is to acquit and find merit. And since the minimum size of a congregation is ten, we have twenty here - ten to condemn and ten to acquit, at the very least.
And from where do we know that a "congregation" means ten? From the verse stated regarding the spies: "How long for this evil congregation". Twelve spies were sent to scout the land, and of them Yehoshua and Calev returned with a good report and are not included in this, leaving ten who were called a "congregation". Therefore, a "congregation" is ten, and two congregations make twenty.
But we have still only reached twenty, so from where do we get another three? The Mishnah deduces from the wording of the verse: "Lo tihyeh acharei rabim leraos" - You shall not follow a multitude to do evil - "shomea ani she'ehyeh imahem letovah" - I deduce that I should be with them for good. This implies that we follow a simple majority for good, to acquit the accused and send him on his way; but for evil, to condemn him, a majority of one vote is not enough.
"Im ken lamah ne'emar 'acharei rabim lehatos'?" - If so, why is it stated, 'to incline after a multitude'? - to teach us that there is a second type of majority, a qualified majority required for a conviction, because "lo kehatayascha letovah hatayascha leraah: hatayascha letovah al pi echad, vehatayascha leraah al pi shenayim" - your inclining for good is not like your inclining for evil: your inclining for good is by one, and your inclining for evil is by two. To tip the scales toward acquittal, an excess of one judge is sufficient; to tip it toward conviction, an excess of two judges is required.
It turns out that against the ten acquitting judges, twelve condemning judges are required, which makes twenty-two. And since "she'ein beis din shakul" - a court cannot be balanced, meaning we do not establish a court with an even number - "mosifin aleihen od echad, harei kan esrim vesheloshah" - we add one more to them, making twenty-three here.
This can be illustrated: in a court of twenty-three, a situation may arise of eleven against twelve, which is enough to acquit but not enough to convict; for a conviction, a majority of thirteen against ten is required. This is the scriptural source, with all its complexity, for a court of twenty-three judges.
A city fit for a Sanhedrin:
There is a Torah commandment, derived through exegesis, to establish a court in every city, in addition to the regional courts and those in Jerusalem. The question arises as to what constitutes the size of a "city": how many residents are required for it to be obligated to have a minor Sanhedrin. The Mishnah presents two opinions on this matter.
The Tanna Kamma says: One hundred and twenty. This number is the minimum number of men required to staff all the positions that halachah requires in a functioning city. With fewer than one hundred and twenty residents, it is impossible to fill all these roles, and the city does not reach the obligation for a court of twenty-three at all, but rather a court of three is established there. This is the breakdown of the calculation:
Twenty-three judges - the members of the minor Sanhedrin itself.
Sixty-nine alternates - three rows of students who sit before the judges, three times the number of judges, who learn the procedures of the law and take the place of the judges when they are unable to serve. That makes ninety-two.
Two court scribes - one writes the words of those who acquit and one writes the words of those who convict. That makes ninety-four.
Two officers - the court officials, who are in charge of executing the judges' rulings, court summonses, and the order of the court. That makes ninety-six.
Two litigants - since there is no trial without at least two litigants. That makes ninety-eight.
Two witnesses - since a person cannot prove his claim with fewer than two. That makes one hundred.
Two refuting witnesses - since testimony is not accepted unless it is subject to refutation, meaning that two others could testify that the first witnesses were not in the place and time they claimed, rendering them conspiring witnesses. That makes one hundred and two.
Two refuting witnesses for the refuting witnesses - since the testimony of the refuting witnesses must also be subject to refutation. That makes one hundred and four.
Ten batlanim - unoccupied men who sit in the synagogue and engage in Torah study, and are always available to complete a minyan for Shacharis, Minchah, and Maariv, so that the Holy One, Blessed is He, so to speak, will not come to the synagogue and fail to find a minyan there. That makes one hundred and fourteen.
Two charity collectors - since charity is not collected by a single individual, to prevent the abuse of authority and for the sake of appearances, as explained in the Mishnah in Tractate Peah. That makes one hundred and sixteen.
A third for distributing the charity - since at the time of distribution, two are not enough, as they judge like a court regarding who is fit to receive and what amount. That makes one hundred and seventeen.
A doctor - That makes one hundred and eighteen.
A scribe - who writes contracts and documents, Torah scrolls, and the like. That makes one hundred and nineteen.
A children's teacher - a melamed. That makes one hundred and twenty.
Rabbi Nechemiah says two hundred and thirty, corresponding to the officers of tens. He has a completely different line of thought: in the division of authority described in the Book of Exodus, "officers of tens" were appointed, each in charge of ten men. Therefore, if twenty-three judges are to serve in the city, each of them must be appointed over ten, and he himself is one of the ten in his group. Twenty-three multiplied by ten - that makes two hundred and thirty, and this is the minimum number of residents that obligates the establishment of a minor Sanhedrin in his opinion.
The halachah follows the Tanna Kamma: one hundred and twenty men who fill all these roles - they are enough to obligate the city in a minor Sanhedrin. With this we conclude, with God's help, the first chapter of Tractate Sanhedrin, and from here we will continue and ascend, with God's help.