According to the agricultural cycle of the Land of Israel, Shemini Atzeret is the last festival of the year. The Torah discusses the festivals in five places, each time highlighting a different dimension. The first two are:

1. Shemot 23:14-19 and
2. Shemot 34:18, 22-26, which briefly mention only the Pilgrimage Festivals.

The first passage speaks of the Festival of Matzot . . . at the appointed time of the month of the springtime (standing grain) . . . and the Reaping Festival [Shavuot] of the first fruits of your produce that you planted in the field, and the Harvest Festival (V’CHAG HA-ASIF) at the end of the year (B’TZET HA’SHANAH), when you gather your produce from the field (23:15-16).

Haamek Davar notes that every agricultural society rightly celebrates these yearly milestones. The Torah’s purpose here is to command us to devote these celebrations to Hashem. During the sabbatical (Shemittah) year however, when no work in the fields is permitted, it might be assumed that the agricultural festivals would be unwarranted. So, the Torah’s restatement of the Pilgrimage Festivals ─
And the Festival of Shavuot shall you make for yourself, with the first fruits of the wheat harvest, and the Harvest Festival (V’CHAG HA-ASIF), shall be at the changing of the year (TEKUFAT HA’SHANAH) (Shemot 34:22)
─ which is mentioned after the sin of the Golden Calf, obligates the observance of the Festivals even during the Shemittah year,
“so that the people will come during the Festival to the Sanctuary, in order to inculcate them with Divine service and faith.”
The significance of the Pilgrimage Festivals therefore transcends the immediately agricultural.

To return to the Festival texts:
3. Vayikra 23:1-44, analyzes all the Festivals, including Rosh Hashanah and Yom Kippur, placing special emphasis on the obligation to refrain from creative work;
4. Bamidbar 28:1-31; 29:1-39, describes the special sacrifices for all occasions, including the basic daily offering and the additional offering of Shabbat and Rosh Chodesh, and all the festivals.
5. Devarim 16:1-17, returns to the subject of the three Pilgrimage Festivals, concentrating on the duties of one who makes the pilgrimage to the Temple in Jerusalem (the Chagigah and other special sacrifices).

In all five passages, Shemini Atzeret is mentioned explicitly only twice. In Vayikra (23:36) we read:
For seven days you shall offer a fire - offering to Hashem; the eighth day is a sacred holiday for you and you shall offer a fire - offering to Hashem. It is a time of retreat (assembly) when you may do no service work.
And in Bamidbar (29:35-38) we learn of the additional sacrifices of Shemini Atzeret. In addition, the Talmud (Sukkah 48a) says that the verse in Devarim (16:15):
and you will be only happy
alludes to the obligation to rejoice on Shemini Atzeret.

What is the significance of Shemini Atzeret, which the Talmud (Yoma 2b-3a, and elsewhere) calls “a festival unto itself”? And, why does it seem to be completely missing from the two passages about the Pilgrimage Festivals in Shemot?

A possible answer might be suggested in a midrash that we have mentioned in past discussions of this holiday. Pesikta Rabbati (addition, ch. 4) says that originally every month during the spring and summer, when Israel’s climate is agreeable, was meant to contain a festival. This began with Pesach during Nisan, Pesach Sheni during Iyar and Shavuot during Sivan, and should have continued through Tammuz, Av and Elul. However, the sin of the Golden Calf nullified the festivals of those months. Subsequently, when Hashem pardoned the people, He “repaid ”them by giving them three festivals in Tishrei: Rosh Hashanah, Yom Kippur and Sukkot. The destruction of the people had been pardoned, but some change in the calendar had to be manifest.

When it came to Tishrei itself, however,
Said the Holy One, Blessed be He, “For others it repays, yet it does not take its own! Give it its own day!”
This day was Shemini Atzeret, the 22nd of Tishrei.

This midrash proposes a pre-Golden Calf scenario which begs further analysis. Had the sin of the Golden Calf never occurred, “Rosh Hashanah” might have been in Tammuz (probably on the 17th, when Moshe brought down the Tablets). Instead of Av being marked by the grief-filled ninth day, it would have included the day of complete purification, Yom Kippur. Elul would have been marked by Sukkot, at a more temperate time of year for dwelling in sukkot.

If Shemini Atzeret did not have to “trail behind” Sukkot, it would be more prominent. Perhaps seeing what Shemini Atzeret might have been had it remained Tishrei’s sole festival might give us insight into what it celebrates, even now.

Although our calendar is primarily lunar, the seasons, which are solar, determine when the three Pilgrimage Festivals fall. It is, therefore, necessary to take the four “turning points” (tekufot) of the earth’s orbit around the sun into account when deciding if a year is to have 12 or 13 months. Based on and the Harvest Festival (V’CHAG HA-ASIF), shall be at the changing of the year (TEKUFAT HA’SHANAH), the Talmud (Sanhedrin 13a) says we do not add a month unless the tekufah of Tishrei (autumnal equinox) would otherwise lack the majority of the month. This means that all of the festival must fall within tekufat Tishrei, when Harvest (HA-ASIF) is still possible. During the Intermediate Days of Sukkot (chol hamo’ed), agricultural work is permitted, but only to prevent a loss.

If, however, there had been no Golden Calf, then
the Harvest Festival (V’CHAG HA-ASIF) at the end of the year (B’TZET HA’SHANAH)
of the first Shemot passage would have been Shemini Atzeret. All harvest ─ not only to prevent a loss ─ would have been permissible up to that festival. “Sukkot of Elul” would then have focused on Hashem’s protection in the wilderness, properly separated from Shemini Atzeret, which alone would have been CHAG HA-ASIF.

As originally envisioned, Shemini Atzeret, “a festival unto itself,” is when an agricultural people rightly thanks Hashem for the year’s produce. It remains the ideal festival for taking stock of both material and spiritual accomplishments, in order to prepare for the winter ahead.