In rabbinic literature, the festival of Shavu’ot is called Atzeret. At first glance, this is surprising. The Torah refers to the last day of Pesaḥ as Atzeret, and refers to the day following the seven days of Sukkot as Shemini Atzeret. Why did the Sages choose to ignore biblical precedent and refer to Shavu’ot as Atzeret?
Let us explore the meaning of the word. “Atzeret” is related to “atzara,” stopping. An Atzeret is a time when many people refrain (i.e., stop themselves) from doing other things, and gather together to celebrate. They then internalize and absorb the messages that the celebration is meant to convey. This helps us to understand why, at the conclusions of Pesaḥ and Sukkot, the Torah prescribes an additional Yom Tov. It is meant as a meaningful send-off for all the pilgrims celebrating near the Temple. It helped them internalize and hold on to their experiences during the holy festival. Even if one missed out on going to Jerusalem, he was required to stop working on the final day of Yom Tov. He needed to internalize all of his spiritual accomplishments and the joy he experienced during the festival, which would then strengthen and elevate him during all the upcoming weekdays.
There was no greater Atzeret in world history than the revelation at Sinai, when all Jews united to accept the Torah. Thus we read: “Israel encamped (va-yiḥan, in the singular) there in front of the mountain” (Shemot 19:2) – as one person with one heart (Rashi). All the other encampments are recorded in the plural, as in every community there are always arguments and disagreements. Only then and there, facing the mountain with the intention of accepting the Torah, were all united. This is the meaning of R. Akiva’s statement: “‘Love your fellow as you love yourself’ (Vayikra 19:18) is a vital principle of the Torah” (Sifra, Kedoshim). It is through the Torah that love and unity are revealed among the Jews, and it is through unity that the Torah is revealed. It was not only the Jews of that generation who were present at Sinai and accepted the Torah, but the souls of all Jews of all times, including those of all future converts. Acceptance of the Torah finally put an end to the defilement which had adhered to them as a result of the sin of Adam and Ḥava (see Shabbat 146a).
The Torah itself refers to the day of Matan Torah as Yom Ha-kahal (the day of assembly), meaning the time when the whole community gathered together, as we read: “the exact words that the Lord had addressed to you out of the fire on the day of the assembly” (Devarim 9:10; see ibid. 10:4 and 18:9).
Actually, the name Shavu’ot has something in common with the meaning of Atzeret, because it indicates summing up and pulling together all the spiritual achievements reached while counting the seven weeks. Since the omer count begins on Pesaḥ, Shavu’ot turns out to be the finale and conclusion of the process that begins with Pesaḥ.
We see that the Sages did not change anything by calling Shavu’ot Atzeret, as Shavu’ot is indeed a festival of gathering and summing up. The Torah’s preference for the name Shavu’ot emphasizes the preparations the Jews underwent before Matan Torah. In contrast, the Sages’ preference for the name Atzeret emphasizes the Jews’ gathering together to absorb the divine overflow that God grants us at the conclusion of the omer period.