35 On the eighth day you shall hold a solemn gathering; you shall not work at your occupations.
ba-YOM ha-sh’-mee-NEE a-TZE-ret tih-YEH la-KHEM kol m’-LE-khet a-vo-DAH LO ta-a-SU
לה בַּיּוֹם הַשְּׁמִינִי עֲצֶרֶת תִּהְיֶה לָכֶם כָּל־מְלֶאכֶת עֲבֹדָה לֹא תַעֲשׂוּ׃
29:35 On the eighth day you shall hold a solemn gathering
This verse mandates an additional “solemn gathering” to be held on the day immediately following the seven days of Sukkot. According to the Sages (Sukkah 55b), the festival of Sukkot has a universal message, demonstrated by the fact that over the course of these seven days, seventy special sacrifices were brought in the Beit Hamikdash, corresponding to the seventy primordial nations of the world. At the completion of the Sukkot holiday, Hashem adds an extra day, as if to say to His people “I don’t want you to leave yet. Let us celebrate one more day together so I can enjoy your exclusive, intimate company.” After celebrating Rosh Hashana, Yom Kippur and finally Sukkot, Hashem doesn’t want the special time to end. He asks His chosen nation to celebrate with Him alone for one more day. This final day is known as Shemini Atzeret, the ‘eighth day of assembly.’