The mitzvah of living in a sukkah is stated in Parshas Emor (Vayikra 23: 42-43 – Artscroll Stone edition translation): “You shall dwell in booths for a seven-day period; every native in Israel shall dwell in booths. So that your generations will know that I caused the Children of Israel to dwell in booths when I took them from the land of Egypt; I am Hashem, your G-d.”
The Shulchan Aruch and Mishnah Berura give the following explanation of this mitzvah: The sukkah represents the Clouds of Glory (Heb. ‘ananei ha-kavod’) in which Hashem protected His children from the heat and sun when He took them out of Mitzrayim. He wanted us to have a life-size replica of these clouds so that we would always remember His awesome wonders. You may be wondering: If Hashem gave us these clouds when we left Mitzrayim, then why don’t we sit in the sukkah around Pesach time? Many answers are given to this question. The most well-known is offered by Tur (14C): Precisely at the time when the weather begins to turn and people leave their summer-dwellings to go back into their homes, we do the opposite. This makes a statement (to ourselves and others) that we are fulfilling the mitzvah of Hashem – not merely acting for our comfort. Were we to sit in sukkos in the beautiful springtime, this message might have been lost! Thus, when we enter the sukkah to fulfill the mitzvah, in addition to the all-important intention of fulfilling a Divine command, we should also think about Yetzias Mitzrayim (the exodus from Egypt) and the miracle of the Clouds of Glory.
The sukkah should be completed as soon as possible after Yom Kippur, following the dictum: ‘Z’rizim makdimin l’mitzvos’ (“Those who are meticulous about mitzvos do them right away.”)
MBY 626:1-3 A sukkah under a tree or roof When the Torah writes the word ‘ba-sukkos’ (in booths), it writes the Hebrew word without the ‘vav’ of the pluralizing suffix. This change suggests a singular sukkah. From this, the Sages derive that a sukkah must stand independently: It may not be under a tree (i.e. even if the tree does not offer much shade – please ask a Rav if you have any concerns about your sukkah!), under a roof, or under another sukkah! In addition, the Sages derive that one’s sukkah must not be his regular home – even if his home happens to be built to the specifications of a sukkah! (Note: This means that at least the schach (sukkah-roof) must be different from his normal roof. It is acceptable, however, to construct a room in one’s house that has a retractable roof and to lay schach over the air-space!)
We will now learn an interesting and important halachic principle concerning the placement of kosher schach: As we will learn in a later lesson, schach material must be of natural vegetative growth that is not attached to the ground. Vines or branches which have grown up and over to cover the sukkah are not kosher for schach; they must be cut from the groundI Now hear this: Even if one were to cover the sukkah with attached braches and then cut them from the ground, the sukkah would still not be kosher! This is derived from the verse (Devarim 16:13): “Make the festival of sukkos for yourself”. The word “make”, say the Sages, implies that the sukkah must be made in a kosher way from the outset, i.e. it must be kosher as soon as it is made! In our case of the attached branches, the sukkah was made first with non-kosher schach and then the schach was altered to become kosher, which is not in keeping with this dictum. In order to rectify the situation, one would need to lift up (albeit momentarily – one-piece at a time) each branch – after being cut – and then place it back down on the sukkah. Now the sukkah is made kosher! (Note: This procedure is not required in all cases. If the schach is kosher from the outset, except that the sukkah was invalid for an external reason – i.e. it was under a tree or a roof etc. – it may be rectified by merely removing the tree or the roof after the sukkah was made, and this would be acceptable, without the need to lift and replace the schach. This distinction is particularly relevant to the retractable roofs mentioned above, or for people who have rain-covers - a.k.a. “shlocks” - for their sukkos which are placed and removed throughout the holiday.)
MBY 627:1-4 Sleeping in a sukkah etc.
Not only must a sukkah be made according to halachic specifications; a person must be sure that he is sitting (or sleeping) directly under the schach of that sukkah, without a barrier! So, for example, were one to be sleeping in a sukkah under a four-poster canopy bed, he would not be fulfilling the mitzvah! Indeed, it is acceptable to erect a tent-like structure overhead, provided that the tent came had slanted panels that came to a pointy top. Similarly, one would not be permitted to stretch a sheet under his schach to protect the people sitting underneath it from rain of the like.
One related issue here is decorations. As we know, decorations are desirable in a sukkah, both on the walls and hanging from the roof. Based upon what we have just learned, certain “guidelines” must be adhered to. We will excerpt here from Guidelines, p. 31, question #61: “Q: How low may the decorations hang? A: A person does not fulfill the mitzvah when sitting underneath an object that is 4 tefachim/handbreadths wide and 4 tefachim from the schach (i.e. vertical distance). Therefore, as a precaution, all decorations should be hung within 32 cm (approx. 12-inches) of the schach even if they are narrow. (If the schach is low, one must be careful to hang the decorations sufficiently high that they are out of reach of young children, who may be tempted to detach them on Shabbos and Yom Tov.) Q: What if the decorations begin within 32 cm but descend below that height? A: This should be avoided if possible.”
MBY 628:1-3 A sukkah under a sukkah (abridged) This short siman is not relevant to most of us; although I am sure it was in earlier times. In the event that you plan on building your sukkah under another sukkah, on top of a wagon or a boat, on camel-back or on a tree-top, please consult the Mishnayos in Maseches Sukkah 1:2 and 2:3 and this siman in the Shulchan Aruch before doing so, and/or ask your local halachic authority. There may be an issue with the validity of your sukkah or its accessibility on Yom Tov, due to Rabbinic restrictions against riding an animal or boat or climbing a tree on Shabbos or Yom Tov!