In order for true unityוְהִנֵּה בִּכְדֵי שֶׁיּוּכַל לִהְיוֹת הַהִתְאַחְדּוּת הָאֲמִתִּית
(and lasting unity) to be forged(וּבַת קַיָּמָא)
among the four categories of Jews,שֶׁל כָּל הַד' סוּגִים דְּיִשְׂרָאֵל,
These two concepts – true unity and lasting unity – are interdependent. For unity to be lasting, it must be true, i.e., it must reflect an essential factor common to all those brought together. Unity that comes as a result of an external factor is dependent upon that factor; when that external factor is absent, the unity will also come to an end.
it must be engendered by teshuvah. Teshuvah means “return,”1 i.e., the soul’s return to its essential G‑dly core.הוּא עַל יְדֵי הַתְּשׁוּבָה.
For teshuvah transcends division.דְּהִנֵּה עִנְיַן הַתְּשׁוּבָה הוּא לְמַעְלָה מֵהִתְחַלְּקוּת,
Every Jew shares the same essential G‑dly core, every Jewish soul is “an actual part of G‑d from Above.”2 As a result, teshuvah erases all divisions among Jews and generates unity.
Therefore, it occurs “in one instant and in one moment,”3שֶׁלָּכֵן הִיא בְּשַׁעְתָּא חֲדָא וּבְרֶגַע חֲדָא.
i.e., teshuvah is essentially above time, making possible the expression of a Jew’s inner G‑dly core, which transcends the limits of this world, including the limits of time and space. Nevertheless, since a Jew lives in this world, within the limits of time and space, teshuvah also takes a measure of time. However, inasmuch as it expresses a Jew’s essential G‑dly core, it is not defined by the ordinary structures of time. Thus, it is not quantified in hours and minutes, but instead, can occur in but one instant and moment.
This constitutes the difference between the First Tablets (which reflect the Torah as it exists in its own right)דְּזֶהוּ הַהֶפְרֵשׁ שֶׁבֵּין לֻחוֹת הָרִאשׁוֹנוֹת (עִנְיַן הַתּוֹרָה מִצַּד עַצְמָהּ)
and the Second Tablets (which reflect the Torah as it is motivated by teshuvah).לַלֻּחוֹת הַשְּׁנִיּוֹת (עִנְיַן תּוֹרָה עַל יְדֵי תְּשׁוּבָה),
This is the reason that the Second Tablets were given on Yom Kippur, the day of teshuvah and forgiveness.
In order to receive the First Tablets, Moshe remained on Mount Sinai for 40 days.שֶׁבִּכְדֵי לְקַבֵּל לֻחוֹת הָרִאשׁוֹנוֹת הָיָה מֹשֶׁה בָּהָר אַרְבָּעִים יוֹם,
Moreover, this was preceded by the seven-week preparatory period of Sefiras HaOmer, the Counting of the Omer, as it is written:4 “You shall count for yourselves seven weeks.”נוֹסָף עַל הַהֲכָנָה דְּשִׁבְעָה שָׁבוּעוֹת תִּסְפָּר לָךְ שֶׁהָיָה לִפְנֵי זֶה.
True, the mitzvah of counting the Omer was given at Mount Sinai when the entire Torah was given. Nevertheless, as Ran writes in his gloss at the end of Tractate Pesachim, the seven-week period from the Exodus until the Giving of the Torah is the source of the mitzvah “You shall count for yourselves seven weeks.” As the Zohar states,5 after the Exodus from Egypt it was necessary that there be seven weeks of preparatory service before the Giving of the Torah. Since the Torah was given within the structures of this world, i.e., time and space, its transmission also involved time.
In contrast, giving the Second Tablets did not involve a protracted period of time. True, Moshe also remained on Mount Sinai for 40 days before receiving the Second Tablets. However,מַה שֶּׁאֵין כֵּן בְּלֻחוֹת הַשְּׁנִיּוֹת,
the purpose of the 40 days during which Moshe remained on the mountain wasהֲרֵי הָאַרְבָּעִים יוֹם שֶׁהָיָה מֹשֶׁה בָּהָר הוּא
(primarily) so that Moshe could motivate the Holy One, blessed be He, to be reconciled with the Jewish people joyously and wholeheartedly.6(בְּעִקָּר) בִּכְדֵי לִפְעֹל שֶׁיִּתְרַצֶּה הקב"ה לְיִשְׂרָאֵל בְּשִׂמְחָה וּבְלֵב שָׁלֵם,
Afterwards, i.e., after Moshe accomplished that reconciliation, the Second Tablets were given in one instant. וּלְאַחֲרֵי זֶה נִתְּנוּ הַלֻּחוֹת בְּשַׁעְתָּא חֲדָא.
For the Second Tablets reflected the Torah as it is connected with teshuvah, which transcends the limits of this material world.
This concept [– that teshuvah occurs in one instant and in one moment –]וְהִנֵּה עִנְיָן זֶה [מַה שֶּׁהַתְּשׁוּבָה הִיא בְּשַׁעְתָּא חֲדָא וּבְרֶגַע חֲדָא]
emphasizes that teshuvah transcends all limits and boundaries.7מַדְגִּישׁ שֶׁעִנְיַן הַתְּשׁוּבָה הוּא לְמַעְלָה מִכָּל מְדִידָה וְהַגְבָּלָה,
For true teshuvah reaches (and encompasses) the innermost dimension and very essence of the soul,מִפְּנֵי שֶׁתְּשׁוּבָה אֲמִתִּית מַגַּעַת (דֶערְנֶעמְט) בִּפְנִימִיּוּת וְעַצְמוּת הַנֶּפֶשׁ,
a dimension that transcends the limits of this world and which is therefore above any division,שֶׁבְּחִינָה זוֹ הִיא לְמַעְלָה מֵהִתְחַלְּקוּת,
the aspect of achas, oneness, described above in sec. 3,בְּחִינַת אַחַת
(and which hence occurs in one instant and in one moment),(בְּשַׁעְתָּא חֲדָא וּבְרֶגַע חֲדָא)
within the soul.דְּנֶפֶשׁ.
On this basis, it is understood that through teshuvah, unity is forged among all the diverse categories of Jews, to borrow the wording of the verse,8וְזֶהוּ מַה שֶּׁעַל יְדֵי הַתְּשׁוּבָה נַעֲשָׂה הַהִתְאַחְדּוּת שֶׁל כָּל הַסּוּגִים דְּיִשְׂרָאֵל,
“from the heads of your tribes… up to and including your wood-hewers and your water-drawers,” comprising all ten categories of Jews9 mentioned in the above verse.מֵרָאשֵׁיכֶם שִׁבְטֵיכֶם עַד חוֹטֵב עֵצֶיךָ וְשׁוֹאֵב מֵימֶיךָ,
Moreover, the unity forged from these categories of Jews is of an essential nature, as reflected in the beginning of the verse7 “You are all standing firmly….”וּבְאֹפֶן דְּאַתֶּם נִצָּבִים כֻּלְּכֶם גו',
Since the verse continues and enumerates all ten categories, why does it begin with “You are all”? Because it highlights the essential core of the soul, which all Jews posess equally.
When that level is tapped, the Jews
“stand firm.”נִצָּבִים מִלְּשׁוֹן נִצָּב מֶלֶךְ,
Moreover, as the term נצבים implies, their firm stance reflects a strength that transcends the limits of this world. Thus, we find the wording10 “the deputy (נצב) of the king,” i.e., the Jews stand firm with the strength of a king.11
The Jewish people become kings and masters over the entire existence of the world.שֶׁיִּשְׂרָאֵל נַעֲשִׂים מְלָכִים אוּן בַּעֲלֵי בָּתִּים עַל כָּל הַמְּצִיאוּת דְּעוֹלָם,
This begins with their being inscribed and sealed for a good and sweet year, with revealed and apparent good, not only in the spiritual sense, but within ten handbreadths of the earth, i.e.,מַתְחִיל מִזֶּה שֶׁהֵם נִכְתָּבִים וְנֶחְתָּמִים בִּכְתִיבָה וַחֲתִימָה טוֹבָה לְשָָׁנָה טוֹבָה וּמְתוּקָה בְּטוֹב הַנִּרְאֶה וְהַנִּגְלֶה לְמַטָּה מֵעֲשָׂרָה טְפָחִים
in material matters, as well. The blessings also encompass the materialגַּם בָּעִנְיָנִים הַגַּשְׁמִיִּים,
because, when this essential level is tapped, there is no distinction between the spiritual and the material,מִכֵּיוָן שֶׁמִּצַּד בְּחִינָה זוֹ אֵין שַׁיָּךְ לְחַלֵּק בֵּין רוּחָנִיּוּת לְגַשְׁמִיּוּת
nor between what is above, in the spiritual realms, and what is below, on this material plane.וּבֵין מַעְלָה לְמַטָּה,
For this rung encompasses the entire Spiritual Cosmos,אוּן דָאס נֶעמְט דוּרְךְ אֶת כָּל סֵדֶר הַהִשְׁתַּלְשְׁלוּת
and, indeed includes even the levels above the Spiritual Cosmos.וְגַם מַה שֶּׁלְּמַעְלָה מִסֵּדֶר הַהִשְׁתַּלְשְׁלוּת.
On this basis, we can understand the Midrashic passage quoted previously: One day, all the daughters came to inquire about the welfare of their father, the king.וְזֶהוּ עִנְיַן יוֹם אֶחָד בָּאוּ כֻּלָּן לִשְׁאוֹל שְׁלוֹם הַמֶּלֶךְ אֲבִיהֶם כו'
In response, the king said: “Let us all make a festival of one day and I will rejoice with them.”נַעֲבֵיד כֻּלָּן חַד יוֹם-טוֹב וְנֶחֱדֵי עִמָּן,
The “one day” (on which all the daughters came to inquire about the welfare of their Father, the King) is Yom Kippur,יוֹם אֶחָד (שֶׁבּוֹ בָּאוּ כֻלָּן לִשְׁאוֹל שְׁלוֹם הַמֶּלֶךְ אֲבִיהֶם) הוּא יוֹם הַכִּפֻּרִים,
referred to as “once a year,” “one” in the realm of shanah, time, for it is a day on which G‑d’s essential oneness is manifest,אַחַת דְּשָׁנָה
(and also “one” in the realms of olam, space, and nefesh, soul).(וְגַם אַחַת דְּעוֹלָם וּדְנֶפֶשׁ),
This is reflected in the service of the Kohen Gadol in the Holy of Holies, as explained above in sec. 3. Since G‑d’s essential oneness is manifest on this day, the essential dimension of every Jew comes to the fore in heartfelt teshuvah, their “inquiry as to the welfare of their Father, the King.”12
From this is drawn forth G‑d’s response, “Let us all make a festival of one day,”וּמִזֶּה נִמְשָׁךְ אַחַר כָּךְ נַעֲבֵיד כֻּלָּן חַד יוֹם-טוֹב כו'
which refers to Simchas Torah,שֶׁקָּאֵי עַל שִׂמְחַת תּוֹרָה,
which is also represents the aspect of “one day” (“one festival”)שֶׁהוּא גַּם כֵּן יוֹם אֶחָד (חַד יוֹם-טוֹב),
a day on which G‑d’s essential oneness – achas – is manifest.בְּחִינַת אַחַת.
The Jews’ celebration of the Giving of the Second Tablets on Yom Kippur – the Torah as it is connected to teshuvah – occurs on Simchas Torah. Hence, all Jews, even those whose connection to the Torah is not evident throughout the year (see above, sec. 1), are inspired to celebrate with the Torah.

Summary

The unity of the Jewish people is brought about through teshuvah, for teshuvah reveals the core of the Jewish soul, which transcends the structures of this world. For this reason, teshuvah occurs “in one instant and in one moment.”
On this basis, we can understand the difference between the Giving of the First Tablets on Shavuos and the Giving of the Second Tablets on Yom Kippur. The First Tablets reflect the Torah as it is drawn into the limits of the world. Hence, they were given after a 40-day period. The Second Tablets, by contrast, were given as a response to the teshuvah of the Jewish people. Hence, they were given “in one instant and in one moment.”
When the essence of the soul is revealed through teshuvah, unity is forged among all the diverse categories that comprise the Jewish people. This in turn draws down a year of blessing and success in both material and spiritual matters.
Since Simchas Torah celebrates the giving of the Second Tablets on Yom Kippur, i.e., the Torah as it is connected to teshuvah, it therefore encompasses the entire Jewish people.