The Zohar says a person who is in the sukkah is under the wings of the Shechinah, and the Gemara (Bava Metzia 85a) tells a related story: Rebbe's sufferings came through an incident and left through an incident. Through what incident did they come? There was a calf being led to slaughter, and it went and hid its head under Rebbe's cloak and cried, not wanting to be slaughtered. Rebbe said to the calf: "Go to slaughter, for this is why you were created – נוֹצַרְתָּ לְכָך!" They said in heaven: since he does not have mercy on creatures, let sufferings come upon him. And through what incident did his sufferings leave? One day, Rebbe's maid was sweeping the house; there were young weasels on the floor, and she was sweeping them away. Rebbe said to her: "Leave them; as it is written: וְרַחֲמָיו עַל כׇּל מַעֲשָׂיו – And His mercies are over all His works. If so, one must have mercy even on young weasels and not sweep them away." They said in heaven: since he has mercy on creatures, let us have mercy on him so that he will not suffer anymore.
Rav Wachtfogel asks, what exactly do they want from Rebbe?! A calf came under his cloak – what could he do with it? Take it with him to his shiur?!
But the Chafetz Chaim says that a person who comes under the roof (or shade) of another person – that person is obligated to provide him protection! Where do we learn this from? Explicit Pesukim in the Torah when the angels came to Lot's house. The townsmen all gathered at the house in an angry fury: וְאַנְשֵׁי הָעִיר אַנְשֵׁי סְדֹם נָסַבּוּ עַל הַבַּיִת. What did they want? הוֹצִיאֵם אֵלֵינוּ וְנֵדְעָה אֹתָם – they wanted Lot to send out the visitors, so they could have their way with them. And what did Lot say to them?
רַק לָאֲנָשִׁים הָאֵל אַל תַּעֲשׂוּ דָבָר כִּי עַל כֵּן בָּאוּ בְּצֵל קֹרָתִי : "These are my guests! You cannot touch them!" This implies that when someone comes under your roof, you are responsible for them!
If so, Rav Wachtfogel says, if a calf comes under your cloak, you are responsible for it! Therefore, since the calf came under Rebbe's cloak and he did not provide it protection and said to it "Go, for this is why you were created!" – he received thirteen years of suffering! And if Hakadosh Baruch Hu acted this way with Rebbe, certainly He will act with us in the same way!
The festival of Sukkot arrives, the Zohar says, and the Shechinah spreads its wings over the sukkah, and therefore when we enter the sukkah, we enter under the protection of Hakadosh Baruch Hu! He is obligated to provide us protection from harm. Therefore, if harm approaches and wants to harm us, Hakadosh Baruch Hu says to them: "They have come under My roof – you have no permission to harm them!"
Thus, during the days of Sukkot, we enter under the shelter of Hakadosh Baruch Hu. We have emerged from Yom Kippur, and now we enter under the צִלָּא דִּמְהֵימְנוּתָא. The first to go into exile were אַבְרָהָם וַחֲמִשָּׁה צַדִּיקַי – Avraham and the five righteous ones. On Sukkot, we too go into exile, and Hakadosh Baruch Hu says: "Whoever comes to Me in the sukkah, I must provide them protection!"
May it be His will that in the merit of sitting in the sukkah, Hakadosh Baruch Hu will grant us a pitzka tava – a good verdict, for a good and sweet year, and may we merit to greet Mashiach Tzidkeinu speedily in our days, Amen v’Amen!
