The Hebrew Calendar is the First Commandment: Parashat Bo 5781

Click the 'play' button below to listen to a recording of Rabbi Yitz Greenberg's Dvar Torah.

Parashat Bo contains the first commandment given to the entire Jewish people as a unit.¹ This foreshadows the full Jewish religion where every aspect of life is guided by Torah and commandments in a covenantal partnership with God.

But which is the first commandment? If one reads the Torah in its plain meaning, the first instruction to the Israelites is in the third verse of chapter 12, to set aside a one year old lamb on the tenth day of Nissan (Exodus 12:3), and slaughter it on the fourteenth. The meat, roasted and eaten together with matzot and bitter herbs, was to be consumed in a family meal and in preparation for the Exodus from Egypt. This sacrificial meal became an annual observance, a recollection and celebration of the Exodus through the generations.²

However, according to the Oral Torah, the rabbinic tradition of interpretation (which our Rabbis teach is revealed at Sinai alongside with the Written Scriptures), the first commandment is found in the second verse, “This month is the beginning of all the months,³ the first month of the months of the year” (Exodus 12:2). This is an instruction that the people of Israel observe their holidays henceforth in accordance with the starting date of the new month. The primary rabbinic court of the Jewish people⁴ decides and declares the day on which the month begins. This is an essential function because the Hebrew calendar month is a lunar month. The moon circles planet Earth and completes a phase cycle (from new moon to new moon) in 29.5 days. Typically the new month is determined by alternating the start of the new month on the 29th day and on the 30th day. This keeps the calendar in sync with the lunar phase cycle.

The instruction serves more than a functional purpose. The holidays are holy days. Behaviors on these days are markedly different than regular days. On the 15th day of Nissan, bread—which is eaten all year long—becomes absolutely prohibited and remains that way for seven days. Matzah, a standard food year round, becomes sacred and elevated to a mitzvah. Work which is permitted every weekday is not to be done on the 15th and 21st of Nissan. On the tenth day of Tishrei, aka Yom Kippur, life actions such as eating, drinking, washing, and sexual activity—which are celebrated and blessed all year long—are prohibited for 24 hours. By moving up the first of the month by a day, or delaying it for a day, the Court is turning a “normal” day into a “holy” day and vice versa.

What makes a day holy? Who creates an obligation to say prayers on a certain day, or to march around with a lulav and etrog, or to stay up all night studying Torah? You might think that God imbues each holy day with a special texture since, after all, God’s commandments determine the special behaviors which we follow. But the Rabbis’ answer is: Judaism is a covenant-partnership in which the human partner plays a central—even authoritative—role. It is the earthly court which decides that Yom Kippur will occur on Tuesday, not Wednesday, thereby endowing that tenth day of Tishrei with sacred character requiring life-altering behaviors and extended prayers. Their decision creates the 24 hours of special closeness to God when the Shekhinah is nigh and receptive to human repentance and piety.⁵

I should add that this mitzvah of calendar setting reflects the Rabbis’ interpretation of the unfolding covenant of Israel. The Rabbis teach that in their times, God self limited further and called the people of Israel to a higher level of partnership authority than in the Bible.⁶ “Rabbi Judah said: ‘These are the festivals of the Land which you shall proclaim’ (Leviticus 23:37). God said: Before Israel became My people, the festivals were ‘the festivals of the Lord.’ But henceforth the festivals are those ‘which you shall proclaim.’”⁷

In another midrash on the verse in our parashah, the Rabbis say: “‘This month shall be unto you’... [Before,] God would watch over everything... When Israel came of age, He handed over everything to them.”⁸ Rabbi Soloveitchik stresses that this commandment represents God handing over final authority in all halakhic matters to the earthly court: “the earthly court decrees, and the Holy One, blessed be He, complies.”⁹ Soloveitchik says that this means that “...Halakhic man received the Torah from Sinai not as a simple recipient but as a creator of worlds, as a partner with the Almighty in the act of Creation.”¹⁰ In my view, this concept of partnership provides the authorization for our Jewish community and its spiritual leadership to uplift the Torah in our day. This includes incorporating leadership of people hitherto excluded, expanding halakhah to include positively the previously marginalized, and creating holy days marking our era’s historical events such as the Holocaust and the creation of the State of Israel.

There is another fundamental teaching embedded in the Hebrew calendar as defined by the Rabbis. While the lunar calendar was widespread, we know that various other calendars were circulating in the Jewish community. The Book of Jubilees (an influential religious text paralleling much of the Book of Genesis and other biblical passages),¹¹ is based on a solar calendar. Likewise, the Greeks and the Romans used a solar calendar.

For the Rabbis, choosing a solar calendar would have coincided with the general culture’s calendar and kept the holidays in their season. A straight lunar calendar was another choice. However, a lunar year is about elven days shorter than a solar year and therefore the months—and dates of holidays—migrate through the year. The Rabbis ruled for a modified lunar calendar so as to preserve the seasonal nature of the holidays.¹² They cited: “Keep the month of Aviv… because in the month of Aviv, God took you out of Egypt…” (Deuteronomy 16:1).¹³ The Rabbis opted for a luni-solar calendar, a lunar months calendar combined with a solar year calendar.¹⁴

Choosing a pure solar calendar would put the Hebrew calendar in lock step with the general culture, but would marginalize the particularist and separate elements in Jewish tradition. These are the elements which motivate Jews to remain a distinctive people, even in the midst of a welcoming general culture. Choosing a pure lunar calendar would represent cutting the Hebrew calendar off from the general culture’s calendar and going into a “time ghetto.” By shaping a luni-solar calendar, the Rabbis assured that Judaism would follow its own path (with holidays not coming out on the same solar date every year). At the same time, by intercalating months, the sacred days would reconnect and interact with the general calendar.

In the past two millennia of Jewish history, the Jews as a minority lived primarily among Christians and Muslims. Had the Jewish calendar been solar they would have been completely at home with Christian time and strongly separated from the Muslim calendar. Had the Hebrew been a purely lunar calendar, the Jews would have been completely at home with Islamic time and strongly separated from the Christian calendar. By choosing a luni-solar calendar, the Rabbis signaled that Jewish religion should be dialectically related to its host cultures. Judaism should maintain its grand vision and not go into a cultural ghetto that would drift toward becoming a tribal, self-centered faith. Judaism should maintain its universal involvement but not give up its particularist values and way of life. The dialectical way is more challenging to live by. However, it enables a constantly renewing culture and faith in which nothing human is alien to it. At the same time, it upholds the uniqueness of Judaism and diversity of humankind’s many tribes.

¹ Earlier commandments were given to individuals. Abraham was commanded to circumcise himself and his sons (Genesis 17:10ff). The Torah tells that after Jacob was wounded in his side, the custom was adopted by the Children of Israel not to eat the sinew of the thigh of kosher animals (Genesis 32:32).

² See Exodus 12:6-11.

³ Setting Nissan, the month of Exodus, as the new New Year going forward is another way of saying that the Exodus is a revolutionary development by which people will measure time in a new way. Compare that during the French Revolution, the Revolutionary Convention established a new calendar to replace the Gregorian calendar. September 22, 1792, the day when the National Convention proclaimed France as a republic was declared Day 1 of Year 1 in the new calendar.

⁴ Such as the Sanhedrin, the Supreme Court in ancient Jerusalem.

⁵ “Seek God when God is [easily] found; call out to Him when He is near” (Isaiah 55:6). God is easily found on the Ten Days of Repentance from Rosh Hashanah to Yom Kippur; see Babylonian Talmud Rosh Hashanah 18a.

⁶ This thesis is spelled out in detail in my book, The Triumph of Life (forthcoming). For now, see my essay on Parashat VaYeitzei, “The Journey to Maturation in the Covenant”, available here: https://www.hadar.org/torah-resource/journey-maturation-covenant.

⁷ Devarim Rabbah 2:14, cited in Joseph B. Soloveitchik’s Halakhic Man, p. 81. According to Soloveitchik, this shift is articulated in the halakhah. The Shabbat grows out of the cosmic process of Creation long before humanity or the Jewish people came into existence. Therefore, Shabbat comes every seventh day without any rabbinic court designation. In the Kiddush and other prayers, we thank and bless God “who sanctifies the Shabbat.” The holidays, on the other hand, grow out of Jewish history (Exodus, Sinai, desert journey, etc.); their actual date of occurrence is set by rabbinic court action. In the Kiddush and liturgy, therefore we thank and bless God “who sanctifies Israel and [who in turn sanctify] the festivals.”

⁸ Shemot Rabbah 15:30. Cited also in Halakhic Man, p. 81.

⁹ Halakhic Man, p. 81.

¹⁰ Halakhic Man, pp. 81-82. Emphasis mine.

¹¹ Dated c. first century BCE but believed to contain earlier material. The Book of Jubilees was not incorporated in the Bible but was influential in its time. It is found among the Dead Sea Scrolls and was referred to by early Christians.

¹² Shavuot in the summer harvest season, Sukkot in the fall harvest season etc. (see e.g. Exodus 23:16).

¹³ Aviv is the early (pre-Babylonian exile) name for Nissan. Aviv also means “spring.”

¹⁴ This is accomplished by intercalating an extra month (Adar II) in 7 out of every 19 years.

Texts Referenced