The sukkah as the shade of emunah

סוכה נק' צלא דמהמנותא בזוה"ק.

The sukkah is called "the shade of faith" (tzila d'mehemnusa) in the holy Zohar.

The Zohar names the sukkah "the shade of emunah," indicating that the sukkah is intimately bound up with the quality of faith.

יתכן לפרש כי כפי האמונה כך נתגלה הקדושה בסוכה כמ"ש במ"א פי' בצלו חמדתי.

It can be explained that according to one's emunah, so is the kedushah (holiness) revealed in the sukkah, as we have explained elsewhere the meaning of "In His shade I delighted" (Shir HaShirim 2:3).

The amount of kedushah a person experiences in the sukkah is proportionate to his emunah — the "shade" of the Divine that one delights in is drawn down by faith.

שע"י אמונת בנ"י זכו שיתגלה הקב"ה ענני כבודו ולהנהיג אותם שלא בדרך הטבע.

For through the emunah of Bnei Yisrael, they merited that Hashem revealed His Clouds of Glory and led them in a manner that was not according to nature.

It was Bnei Yisrael's faith in following Hashem into the wilderness that drew down the Ananei HaKavod and the supernatural guidance commemorated by the sukkah.

לכן כתיב חסד נעוריך שהי' ע"י התעוררות שלהם.

Therefore it is written, "the kindness of your youth" (Yirmiyahu 2:2) — for it came about through their own arousal.

The "chesed of your youth" praises Bnei Yisrael's initiative; the revelation came in response to their own awakening of faith, an arousal from below.

וכן איתא בשם הבעש"ט פי' ה' צלך כפי הנהגת האדם כך מתגלה עליו צל הקב"ה:

And so it is brought in the name of the Baal Shem Tov, the explanation of "Hashem is your shade" (Tehillim 121:5): according to a person's conduct, so is the "shade" of Hashem revealed upon him.

The Baal Shem Tov reads "Hashem is your shade" to mean that Hashem mirrors a person's own conduct — like a shadow, Hashem's revealed relationship to a person tracks that person's own avodah and emunah.

Summary: The sukkah is "the shade of emunah" because the degree of kedushah revealed within it corresponds to one's faith. It was the emunah of Bnei Yisrael — their willingness to follow Hashem into the desert — that drew down the supernatural Clouds of Glory, an arousal from below. As the Baal Shem Tov taught on "Hashem is your shade," Hashem reveals Himself to a person in measure with that person's own conduct.