The Jewish calendar is lunisolar. This means that the length of Jewish months are determined by the cycles of the moon. But a moon cycle is about 29.5 days long, which means twelve lunar months come out to be about 354 days — 11 days shorter than a solar year. For this reason, leap months are added to the calendar from time to time so that all the festivals remain in their appropriate seasons; this is called intercalation. Today, Jews have a fixed schedule for intercalating the calendar, adding seven leap months (always a second month of Adar in late winter) distributed over every 19 years.
The Mishnah was penned before the fixed schedule was in place, when the decision to declare a leap year had to be made on an annual basis. Although the Torah does not mention anything specifically about adding a leap month, it does assign festivals to meteorological and agricultural seasons, thereby necessitating the practice. As Rosh Hashanah 21 reports:
Rav Huna bar Avin sent to Rava: When you see that the season of Tevet (i.e., winter) will extend to the 16th of Nisan, add an extra month to that year. And do not worry about finding an additional reason to justify making it a leap year, as it is written: “Observe the month of spring.” (Deuteronomy 16:1). That is to say, see to it that the spring (i.e., the spring equinox) is in the first half of Nisan.
The month of Nisan is referred to as the month of spring in the Torah. Passover, which begins on the 15th of the month, is a spring holiday. As a result, winter must end by the 15th of Nisan, the first day of Passover. If the spring equinox is going to fall on the 16th of Nisan or later, Rav Huna says that we intercalate the calendar by repeating the month that precedes Nisan (Adar) to prevent this from happening.
The opening mishnah of Sanhedrin presents two opinions about the courts that make this happen. Rabbi Meir makes it simple. In his view, a panel of three judges can determine if a leap month is needed. Rabban Shimon ben Gamliel, however, presents a more complicated process:
The deliberations begin with three judges, and they debate the matter with five judges, and they conclude the matter with seven judges.
How does this work? A beraita on today’s daf explains. If only one member of the three judge panel believes there is reason to consider intercalating the calendar, they are outvoted by the other two, and the matter is settled — the year is not intercalated. If two (or more) think that a discussion is in order, they invite two additional judges to join the deliberations. Similarly, if three or more (a majority) of the five-member judicial panel vote to intercalate the year, then two more members are added to the panel. This final panel of seven judges considers the recommendation and, if accepted, issues a declaration that a leap month will be added to the calendar. Rabban Shimon ben Gamliel’s position was ultimately adopted into law. The resulting process may be more cumbersome to implement, but it ensures a more deliberative process.
The Gemara wonders about why Rabban Shimon ben Gamliel’s judicial panels contain three, five and seven judges respectively. That they are each an odd number is both logical and practical — it prevents tie votes. But why these numbers in particular?
Two opinions are provided, those of Rabbi Yitzhak bar Nahmani and Rabbi Shimon ben Pazi, although we are not sure which view goes with which. One says that they correspond to three different groups, mentioned in parallel sections of the books of Second Kings and Jeremiah which report about the fall of the Kingdom of Judah and the destruction of the First Temple. The three judge panel corresponds to three guards who stood at the threshold to the Temple (see II Kings 25:18 and Jeremiah 52:24), five corresponds to five royal privy councilors (literally, those who saw the king’s face) as reported by Second Kings (25:19), and seven corresponds to Jeremiah’s count which puts this group at seven (see Jeremiah 52:25). The Bible tells us little about what these groups did and certainly does not indicate that they were responsible for decisions about the calendar. But this explanation roots the structure of the rabbinic calendar courts in the biblical text by finding groups of three, five and seven people in the text.
The second opinion also relies on a numeric correspondence, but, in this case, a poetic one. It suggests that three numbers were chosen for the calendrical deliberations because they correspond to the number of Hebrew words in each of the three verses of the priestly benediction (Numbers 6:24–26). Hebrew is a terser language than English, so it’s not easy to translate these lines into English using only three, five and seven words respectively, but even in translation you can see that they increase in length:
May God bless you and keep you.
May God deal kindly and graciously with you.
May God bestow God’s kindness upon you and grant you peace.
In biblical and rabbinic times (and increasingly in our day as well), people were attuned to the benefit of predictable seasonal weather patterns. Syncing up the seasons to the holidays that celebrated them strengthened the connections between the religious and agricultural calendar. How fitting, therefore, that the inspiration for the size and shape of the courts that allowed folks to celebrate the bounty of the land in the proper season be attributed to verses that remind us that God is the source of all blessings.
Read all of Sanhedrin 10 on Sefaria.
This piece originally appeared in a My Jewish Learning Daf Yomi email newsletter sent on December 27, 2024. If you are interested in receiving the newsletter, sign up here.
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