The sukkah as testimony to true judgment

סוכה היא עדות לבנ"י שנטהרו מחטאם.

The sukkah is a testimony for Bnei Yisrael that they have been purified from their sin.

Sukkos follows immediately after Yom Kippur. The mitzvah of sukkah bears witness that Bnei Yisrael have been cleansed of their sins through the teshuvah of the Yamim Noraim.

כדאיתא בגמ' לעתיד לבוא אומות רוצין לשוב והש"י נותן להם מצות סוכה כו'.

As it is found in the Gemara, that in the future the nations will wish to return (to Hashem), and Hashem will give them the mitzvah of sukkah, etc. (Avodah Zarah 3a).

The Gemara relates that in the time to come the nations will ask for a chance to serve Hashem, and He will give them the "easy" mitzvah of sitting in a sukkah as a test.

והפי' כי כל בע"ת הוא בחסד עליון שהקב"ה פושט יד לקבלו ולפנים משורת הדין.

And the explanation is that every ba'al teshuvah (penitent) is (received) through supernal kindness (chesed elyon), in that the Holy One, blessed be He, extends His hand to receive him, going beyond the letter of the law (lifnim mi-shuras ha-din).

Teshuvah itself is an act of Divine grace. By strict justice a sinner might have no way back, but Hashem reaches out and accepts the penitent lifnim mi-shuras ha-din — beyond what the law would require.

וע"ז טוענין הרשעים.

And concerning this the wicked make a claim.

The nations (the "wicked") will argue: if teshuvah is accepted purely by Divine kindness beyond the law, then we too deserve to be received back, just like Israel.

והתשובה כי הקב"ה דיין אמת.

And the answer is that the Holy One, blessed be He, is a true Judge (dayan emes).

The response to their claim: Hashem judges truthfully. His acceptance of penitents is not arbitrary favoritism but a true judgment that distinguishes who genuinely belongs.

ומי שיש בו נקודה פנימיות לטוב רק שאינו יכול להוציא מכח אל הפועל השי"ת עוזר לו.

And one who has within him an inner point (nekudah penimiyus) directed toward good, only that he is unable to bring it from potential into actuality — Hashem helps him.

The real criterion is the inner point. Whoever carries within him a genuine nekudah penimiyus yearning for good, but cannot actualize it on his own, receives Hashem's help to draw it out. Teshuvah is accepted where that inner spark of good truly exists.

וכיון שיכול להיות תחת צלו ית' הוא סימן שיש בו נקודה של אמת כמ"ש [בזוה"ק] מאן דהוא מגזעא ושרשא דישראל ישבו בסוכות כו'.

And since one is able to be under His shade (the shade of the sukkah), it is a sign that there is within him a point of truth (nekudah shel emes), as it says [in the Zohar]: "whoever is of the stock and root of Yisrael shall dwell in sukkos."

The sukkah is the test: being able to dwell under the shade of Hashem's protection proves one possesses an inner point of truth. The Zohar teaches that only one rooted in the source of Israel can truly sit in the sukkah's holy shade.

והרשעים א"י להיות בסוכה כדכתיב לא יגורך רע.

And the wicked are unable to be in the sukkah, as it is written: "Evil shall not dwell with You" (Tehillim 5:5).

One who lacks that inner point of good cannot endure within the sukkah's holy shade, for evil has no abode in Hashem's presence. This is why the sukkah test exposes the nations who only outwardly claim to return.

וזה טעם מצות סוכה אחר המשפט בר"ה ויוכ"פ שהוא עדות על המשפט אמת:

And this is the reason for the mitzvah of sukkah coming after the judgment of Rosh Hashanah and Yom Kippur — for it is a testimony to the true judgment (mishpat emes).

Sukkos is placed right after the judgment of the Yamim Noraim because dwelling in the sukkah confirms the verdict: those who can sit in Hashem's shade are shown to possess the inner point of truth, testifying that His judgment of who was purified is a mishpat emes — a true judgment.

Summary: The sukkah testifies that Bnei Yisrael were purified on Yom Kippur. Although teshuvah is granted through supernal chesed, beyond the letter of the law, Hashem remains a true Judge: He helps only the one who possesses an inner nekudah of good and truth that he cannot actualize alone. The sukkah is the proof — only one rooted in the source of Israel can dwell in its holy shade, since "evil shall not dwell with You." Placed right after the judgment of Rosh Hashanah and Yom Kippur, the sukkah is the testimony that Hashem's verdict is a true judgment.