The eighth day shall be a solemn assembly [in Hebrew, "atzeret"] for you. (Deut. 29:35)

According to the plain meaning of the text, the word "atzeret" means "to be prevented from performing one's regular work". In Kabbalah, the word "atzeret" is a term describing "Knesset Yisrael", the spiritual concept known as "Congregation of Israel". Were it not for this concept, represented by the Jewish people, the whole universe would lack meaning and purpose. It is also an expression denoting malchut, i.e. authority, dominion.

For the above-mentioned reasons Shemini Atzeret is a festival all by itself. Among the four species, it corresponds to the etrog, which represents the Jewish people and which is held separately, i.e. in a different hand than the other three. The Shemini Atzeret holiday is related to the festival of the giving of the Torah, Shavuot, which the Talmud always refers to as "Atzeret". We find the name "atzeret" also applied by the Torah to the Seventh day of Passover (Deut. 16:6), although that day is an integral part of the festival. Thus, the term appears in connection with all three pilgrimage holidays.

What does all this mean? Just as the word "Shabbat" is applied by the Torah to the various festivals on various occasions to show that the Jewish Nation is the "bride" of the Shabbat, so the word "atzeret", when used in connection with the festival, conveys the idea that the Jewish people, spiritually speaking, are the purpose of all these festivals. In Kabbalistic terms, they are the yesod, the "foundation", without which the entire legislation of the festivals would lack meaning.

[Selected with permission from the seven-volume English edition of "The Torah Commentary of Rebbeinu Bachya" by Eliyahu Munk.]