There was once a king who invited his children for a banquet of several days. When it came time for them to go, he said to them: “My children, please, stay with me one more day—your parting is difficult for me…”
Rashi, Leviticus 23:36
With this parable, our sages explain the significance of Shemini Atzeret. Shemini Atzeret (literally, “the eighth of retainment”) is the one-day festival that immediately follows the seven-day festival of Sukkot. Sukkot is a week-long reunion banquet that the supernal King throws for His children, the souls of Israel; for seven days we rejoice in our kinship with G-d and with each other. But then, when it comes time for us to take leave of the festival and return to our everyday pursuits, G-d requests: “Stay one more day…” Hence, the festival of Shemini Atzeret, one more day of joy and fellowship in the divine palace before returning to the hinterland of material life.
But let us examine this parable more closely. At first glance, the king’s request seems little more than an indulgence of sentiment. If his children’s return to their lives apart from him is inevitable, what is gained by staying one more day? Other than delaying the pain of parting for several hours, is there anything of enduring significance in an “eighth day of retainment”?
In the parable, our sages do not have the king say, “our parting is difficult for me,” but “your parting is difficult for me.” Indeed, G-d, of whom “no place is void of Him,” never parts from us. It is we who might “part” from Him, moving on to a state of diminished awareness of our relationship with Him.
“Your parting” has yet another meaning: our parting from each other, which, in G-d’s eyes, is synonymous to our parting from Him. When the people of Israel are one with G-d, they are also one with each other, united as children of their royal father. The same applies in reverse: when the people of Israel are one with each other, united in their common identity as G-d’s children, they are one with G-d.
Sukkot, more than any other festival, emphasizes the unity between Jew and Jew achieved through the Jew’s relationship with G-d. All mitzvot have this uniting effect, underscoring our common endeavor to fulfill the will of our Father in Heaven; but the mitzvah of sukkah is unique in the depth and scope of the unity it awakens amongst us.
When two Jews study a chapter of Torah, they strengthen their relationship with G-d and with each other by integrating the wisdom of G-d into their minds and lives; but their study also underscores the differences between them, as each understands and appreciates the divine wisdom in accordance with his distinct intellectual prowess and spiritual sensitivity. When two Jews fulfill the divine command to give charity, the deed differentiates even as it unites, as each gives in accordance with his generosity and financial capacity. The same is true of virtually every other mitzvah: while a mitzvah unites diverse individuals in the common pursuit of serving the divine will, it also accentuates the diversity of talent, experience and commitment that each bring to the deed.
The sukkah, however, is the ultimate equalizer. This mitzvah is observed by dwelling in a bough-covered hut for seven days—eating, sleeping, and socializing in it, and otherwise regarding it as one’s home, for the duration of the festival. In other words, the mitzvah of sukkah is not about what you do and how you do it, but where you do whatever it is that you do. Two people thinking the same thought are nevertheless thinking differently; the same is true of two people experiencing the same feeling or doing the same deed. But two people inhabiting a particular place are utterly synonymous in the fact of their presence: neither can be more or less or differently there (in the empirical, physical sense) than the other. So the sukkah relates to all its inhabitants equally: it is the scholar’s home no more and no less than it is the simple laborer’s; the mystic and the businessman, the scientist and the artist, are housed by its walls without regard to the nature and content of their lives. In the words of the Talmud, “All of Israel might conceivably dwell in a single sukkah.”
The Eighth of Retainment
But the sukkah is a once-a-year experience; indeed, the halachic definition of the sukkah is “a temporary dwelling” (dirat arai). After the seven-day unity fest is over, the Jew moves from the sukkah back to his home: back to a life in which his place of habitat is no longer a mitzvah, a primary element in his relationship with G-d; back to a life in which his oneness with his fellow Jews is expressed via the more “individualistic” mitzvot of thought, word and deed.
Yet our parting is distressful to G-d. So He retains us one day longer, for an “eighth day of retainment.”
He retains us for an “eighth day” of Sukkot—a day on which dwelling in the sukkah is no longer a mitzvah but on which the unity of Sukkot suffuses us nonetheless. A day on which we are utterly and unequivocally one without the paraphernalia of oneness, without the need for an actual edifice to context our unity.
He retains us for a day of “retainment”—a day on which it is not we who are in the sukkah but the sukkah that is within us. A day on which we are empowered to imbibe and internalize the unity of Sukkot, to store it in the pith of our souls so that we may draw on it in sukkah-less months to come.
Based on the Rebbe’s talks on Simchat Torah of 5716 (1955) and on other occasions
 Zohar, Tikkunim 57; cf. Midrash Rabbah, Bamidbar 12:4.
 Thus, before the Jew approaches G-d in prayer, he pledges: “I hereby accept upon myself the commandment `Love your fellow as yourself.’ ”
 Talmud, Sukkah 27b. This is more than a hypothetical possibility—it is the basis for one of the laws that govern the sukkah‘s construction. The Torah sets all sorts of specifications for the sukkah‘s size and construction: its roof of branches must yield “more shade than sun”; it must have a minimum of two full walls plus part of a third; its ceiling must may be no lower that ten tefachim (approx. 32 inches) and no higher than 20 amot (approx. 31.5 feet); its area must be no less than seven tefachim by seven tefachim; etc. However, there is no maximum limit for the size of the sukkah‘s area—one can make his sukkah as long and as broad as he desires. This is derived from the verse (Leviticus 23:42), “… for seven days, all citizens of Israel shall dwell in sukkot.” In this verse, the word sukkot, which is the plural of sukkah, is spelled without the letter vav; this means that the word can also be read as sukkat, “the sukkah [of],” in the singular. Explains the Talmud: the Torah wishes to imply that “the entire nation of Israel may dwell in a single sukkah.”
 In all Jewish communities outside the land of Israel, Shemini Atzeret is actually observed for two days. This is in commemoration of the time when the Jewish calendar was set on a monthly basis by the sanhedrin in Jerusalem, and all diaspora communities, who received word of the exact date of the festival days or weeks later, observed an additional day of each festival out of doubt. Thus, the seven-day festival of Passover was observed for eight days, the one-day festivals of Rosh Hashanah and Shavuot for two days, etc. On Sukkot, the matter was more complicated: the Torah ordains a seven-day festival, followed by the single day of Shemini Atzeret; thus the diaspora observed a total of nine days—seven days of Sukkot, an eighth day which might have been the last day of Sukkot or Shemini Atzeret, and a ninth day, which might have been the “real” Shemini Atzeret. Today, we follow a fixed calendar, so we are no longer in doubt of the festivals’ true dates; nevertheless, having gained extra days of holiness in our calendar, we are loath to give them up, and follow the custom of our ancestors. We, too, observe two days of Shemini Atzeret, on the eighth and ninth days from the first day of Sukkot (the second day of Shemini Atzeret is called Simchat Torah).
On the question of whether one should dwell in the sukkah on the first day of Shemini Atzeret, which is the offspring of the possible last day of Sukkot, the Talmud rules: “One dwells in the sukkah, but one does not recite the blessing” on the sukkah recited on the first seven days, in order to emphasize that the mitzvah of sukkah, as commanded by the Torah, extends only for seven days (Talmud, Sukkah 46b-47a; see Shulchan Aruch and commentaries, Orach Chaim 668:1). Thus, we have seven days of full-fledged dwelling in the sukkah, followed by the first day of Shemini Atzeret, on which we dwell in it but emphasize that this is not a mitzvah, followed, in turn, by the second day of Shemini Atzeret, on which we do not dwell in the sukkah at all.
The deeper significance of this is that the unity achieved by the sukkah also has these three phases: (a) the seven days of Sukkot, on which the mitzvah of sukkah unites us; (b) the first day of Shemini Atzeret, on which dwelling in the sukkah is no longer a mitzvah, yet we retain the essence of sukkah and express it with our custom of dwelling in the sukkah one more day; (c) the second day of Shemini Atzeret, on which we have internalized the unity of sukkah to such an extent that there is no need for any “symbolic” expression of it—indeed, no symbol or act can possibly embody its depth and scope, which transcends any and all representation.
 Likkutei Sichot, vol. II, pp. 433-434; ibid., vol IX, pp. 225-236.