תשבו. כעין תדורו מכאן אמרו כל ז' ימים עושה סכתו קבע וביתו עראי כיצד אוכל ושותה ומטייל בסוכה ומעלה כליו הנאים לסוכה כו'.
18th century commentary from the Vilna Gaon.
(א) סֻכָּה שֶׁהִיא גְבוֹהָה לְמַעְלָה מֵעֶשְׂרִים אַמָּה, פְּסוּלָה. רַבִּי יְהוּדָה מַכְשִׁיר. וְשֶׁאֵינָהּ גְּבוֹהָה עֲשָׂרָה טְפָחִים, וְשֶׁאֵין לָהּ שְׁלֹשָׁה דְּפָנוֹת, וְשֶׁחַמָּתָהּ מְרֻבָּה מִצִּלָּתָהּ, פְּסוּלָה.
(1) A sukka, i.e., its roofing, which is the main and most crucial element of the mitzva, that is more than twenty cubits high is unfit. Rabbi Yehuda deems it fit. Similarly, a sukka that is not even ten handbreadths high, and one that does not have three walls, and one whose sunlight that passes through its roofing is greater than its shade are unfit.
Rava said that the halakha is derived from here: “In sukkot shall you reside seven days” (Leviticus 23:42). The Torah said: For the entire seven days, emerge from the permanent residence in which you reside year round and reside in a temporary residence, the sukka. In constructing a sukka up to twenty cubits high, a person can render his residence a temporary residence, as up to that height one can construct a structure that is not sturdy; however, in constructing a sukka above twenty cubits high, one cannot render his residence a temporary residence; rather, he must construct a sturdy permanent residence, which is unfit for use as a sukka.
(ט) כָּל שִׁבְעַת הַיָּמִים אָדָם עוֹשֶׂה סֻכָּתוֹ קֶבַע וּבֵיתוֹ עֲרַאי. יָרְדוּ גְשָׁמִים, מֵאֵימָתַי מֻתָּר לְפַנּוֹת, מִשֶּׁתִּסְרַח הַמִּקְפָּה. מָשְׁלוּ מָשָׁל, לְמָה הַדָּבָר דּוֹמֶה, לְעֶבֶד שֶׁבָּא לִמְזוֹג כּוֹס לְרַבּוֹ, וְשָׁפַךְ לוֹ קִיתוֹן עַל פָּנָיו:
(9) All seven days of Sukkot, a person renders his sukka his permanent residence and his house his temporary residence. If rain fell, from when is it permitted to vacate the sukka? It is permitted from the point that it is raining so hard that the congealed dish will spoil. The Sages told a parable: To what is this matter comparable? It is comparable to a servant who comes to pour wine for his master, and he pours a jug [kiton] of water in his face to show him that his presence is not desired. So too, in the sukka, rain is an indication that the Holy One, Blessed be He, does not want the person to fulfill the mitzva of sukka.
(2) All seven days [of the festival] a man must make the sukkah his permanent residence and his house his temporary residence. The essential commandment of the sukkah is that one should live in it during Sukkot as one lives in a permanent home the rest of the year. In the time of the Mishnah and Talmud this meant that one would sleep and eat in the sukkah. It also meant that they would bring their regular belongings, beds, mattresses, pillows, blankets, etc. out into the Sukkah. Today it means that any activity that one can do with comfort in the sukkah, should be done there. It means inviting over company and sitting there instead of inside in the living room. It means playing games with the children in the sukkah. It means reading there, if the lights are good enough. It means striving to spend as much time in the sukkah as possible and not turning it into just a dining room.
(ג) ושפך לו. רבו קיתון על פניו של עבד, כלומר אי אפשי בשמושך. אף כאן גשמים הללו מראין שאין הקב״ה מקבל מעשיהם ברצון:
(3) ושפך לו - his master a pitcher on the face of the servant, that is to say, I have no use for your service, even here, these rains show that the Holy One, blessed be He does not accept their deeds with favor.
(3) If rain fell, when may one be permitted to leave it? When the porridge becomes spoiled. They made a parable. To what can this be compared? To a slave who comes to fill the cup for his master, and he poured a pitcher over his face. This parable is fascinating for its simplicity and intricacy. The sukkah is in its essence a prayer for rain after all, Sukkot is the beginning of the rainy season. Yet we don’t want rain while sitting in the sukkah. Hence early rain is perceived as an insult and not as a blessing. We can see from the parable just how sensitive the issue of rain was, and still is, to those living in the land of Israel.
The Sukkah is a temporary structure which we relate to as permanent. We are תשבו כעין תדורו [tashvu k'ein taduru], we sit in the sukkah in the manner in which we dwell in our permanent we homes, and each Jew is commanded to עושה סוכתו קבע וביתו עראי [oseh sukato keva u'veito arai], to eat, sleep, and sit in the sukkah in a manner of קבע [keva], permanence, though the Sukkah itself is עראי [arai], temporary. (Sukkah 26b). There is no attempt to deny the fact that this is a temporary structure, no demand to actually move into the Sukkah, but to sit in it כעין תדורו [k'ein taduru], “like the way you dwell”. You are sitting in a temporary hut, fully cognizant of its temporary nature, but you are relating to it as if it is permanent... We are commanded to treat a temporary object with permanence."
...We sit flush with the world, in a ‘house’ that calls attention to the fact that it gives us no shelter. It is not really a house. It is the interrupted idea of a house, a parody of a house… It is like that architectural feature called the broken pediment, the notch in the roofline of the facade of a house which leaves the mind to complete the line, and thus implants the idea of a line in the mind even more forcefully than an unbroken line would. So it is that the sukkah, with its broken lines, its open roof, its walls that don’t quite surround us, calls the idea of the house to mind more forcefully than a house itself might do.
And it exposes the idea of a house as an illusion. The idea of a house is that it gives us security, shelter, haven from the storm. But no house can really offer us this. No building of wood and stone can ever afford us protection from the disorder that is always lurking all around us. No shell we put between us an the world can ever really keep us secure from it. And we know this. We never really believed this illusion. That’s why we never felt truly secure in it [...]
In the sukkah, a house that is open to the world, a house that freely acknowledges that it cannot be the basis of our security, we let go of this need. The illusion of protection falls away, and suddenly we are flush with our life, feeling our life, following our life, doing its dance, one step after another.
(ז) לֵ֣ךְ אֱכֹ֤ל בְּשִׂמְחָה֙ לַחְמֶ֔ךָ וּֽשֲׁתֵ֥ה בְלֶב־ט֖וֹב יֵינֶ֑ךָ כִּ֣י כְבָ֔ר רָצָ֥ה הָאֱלֹהִ֖ים אֶֽת־מַעֲשֶֽׂיךָ׃ (ח) בְּכָל־עֵ֕ת יִהְי֥וּ בְגָדֶ֖יךָ לְבָנִ֑ים וְשֶׁ֖מֶן עַל־רֹאשְׁךָ֥ אַל־יֶחְסָֽר׃ (ט) רְאֵ֨ה חַיִּ֜ים עִם־אִשָּׁ֣ה אֲשֶׁר־אָהַ֗בְתָּ כָּל־יְמֵי֙ חַיֵּ֣י הֶבְלֶ֔ךָ אֲשֶׁ֤ר נָֽתַן־לְךָ֙ תַּ֣חַת הַשֶּׁ֔מֶשׁ כֹּ֖ל יְמֵ֣י הֶבְלֶ֑ךָ כִּ֣י ה֤וּא חֶלְקְךָ֙ בַּֽחַיִּ֔ים וּבַעֲמָ֣לְךָ֔ אֲשֶׁר־אַתָּ֥ה עָמֵ֖ל תַּ֥חַת הַשָּֽׁמֶשׁ׃ (י) כֹּ֠ל אֲשֶׁ֨ר תִּמְצָ֧א יָֽדְךָ֛ לַעֲשׂ֥וֹת בְּכֹחֲךָ֖ עֲשֵׂ֑ה כִּי֩ אֵ֨ין מַעֲשֶׂ֤ה וְחֶשְׁבּוֹן֙ וְדַ֣עַת וְחָכְמָ֔ה בִּשְׁא֕וֹל אֲשֶׁ֥ר אַתָּ֖ה הֹלֵ֥ךְ שָֽׁמָּה׃ (ס)
(7) Go, eat your bread in gladness, and drink your wine in joy; for your action was long ago approved by God. (8) Let your clothes always be white, and your head never lack oil. (9) Enjoy happiness with a woman you love for all the fleeting days of life that have been granted to you under the sun—all your fleeting days. For that is your portion in life, from the labor you do under the sun. (10) Whatever it is in your power to do, do with all your might. For there is no action, no reasoning, no knowledge nor wisdom in Sheol, where you are going.
Shnei Luchot HaBrit (ShLaH), Rabbi Isaiah Horowitz (1565?-1630, Prague/Germany/Israel), Masechet Sukkah, Derech Chayim Tochachot Mussar
…And I will tell you that my heart always burns when I see the people of Israel building houses like the castles of princes, making for themselves a permanent dwelling in this world upon the tainted earth…as if this were the inheritance they should give to their children, and their children’s children, for all eternity…Therefore, if God gives you great wealth, build houses according to your needs and not more. Do not build towers and walls in pride and grandeur, only a dignified dwelling-place with a room in it to be alone for the purpose of Torah study and repentance…
(Text discovered on T'ruah Sukkot Resource)
(מג) לְמַ֘עַן֮ יֵדְע֣וּ דֹרֹֽתֵיכֶם֒ כִּ֣י בַסֻּכּ֗וֹת הוֹשַׁ֙בְתִּי֙ אֶת־בְּנֵ֣י יִשְׂרָאֵ֔ל בְּהוֹצִיאִ֥י אוֹתָ֖ם מֵאֶ֣רֶץ מִצְרָ֑יִם אֲנִ֖י יְהֹוָ֥ה אֱלֹהֵיכֶֽם׃