This is the meaning of the text of the various blessings pronounced before one fulfills a mitzvah: “[Blessed be He,] Who has betrothed us by His commandments,”

וְזֶהוּ שֶׁאוֹמְרִים: "אֲשֶׁר קִדְּשָׁנוּ בְּמִצְוֹתָיו",

The Hebrew word kideshanu—generally rendered “Who has sanctified us”—is here rendered “Who has betrothed us,” from the Hebrew word kiddushin (“betrothal”), for mitzvot too, are:

like a man who betrothes a wife so that she be united with him in a perfect bond, as it is written, “And he shall cleave to his wife, and they shall be one flesh.”13

כְּאָדָם הַמְקַדֵּשׁ אִשָּׁה לִהְיוֹת מְיוּחֶדֶת עִמּוֹ בְּיִחוּד גָּמוּר, כְּמוֹ שֶׁכָּתוּב: "וְדָבַק בְּאִשְׁתּוֹ וְהָיוּ לְבָשָׂר אֶחָד". –

Exactly similar to the unity achieved through betrothal, and even infinitely surpassing it, is the union of the divine soul that is engaged in Torah and the commandments, and of the vivifying soul, and their garments referred to above, viz., thought, speech, and action—all of them becoming united with the light of the blessed Ein Sof.

כָּכָה מַמָּשׁ וְיֶתֶר עַל כֵּן לְאֵין קֵץ, הוּא יִחוּד נֶפֶשׁ הָאֱלֹהִית הָעוֹסֶקֶת בַּתּוֹרָה וּמִצְוֹת וְנֶפֶשׁ הַחִיּוּנִית וּלְבוּשֵׁיהֶן – הַנִּזְכָּרִים לְעֵיל – בְּאוֹר־אֵין־סוֹף בָּרוּךְ־הוּא.

This spiritual union infinitely surpasses the physical union of man and wife. The correlation to a physical union is valid only in the sense that in this world, there can be no greater union than that of man and wife. This union is termed kiddushin.

Therefore did Solomon, peace unto him, in the Song of Songs compare this union of G-d and Jews through Torah and mitzvot with the union of bridegroom and bride,

וְלָכֵן הִמְשִׁיל שְׁלֹמֹה עָלָיו הַשָּׁלוֹם בְּ"שִׁיר הַשִּׁירִים", יִחוּד זֶה לְיִחוּד חָתָן וְכַלָּה,

this union being with attachment—an external level of unity, with longing—a more inward level of unity, and desire—an even more inward level of unity, with embrace and kissing.

בִּדְבִיקָה חֲשִׁיקָה וַחֲפִיצָה בְּחִיבּוּק וְנִישּׁוּק.

All the above manners of union are found in the Jew’s relationship to G-d through Torah and mitzvot.

Until now, the Alter Rebbe expounded on the theme of unity, understanding kideshanu as deriving from kiddushin (“betrothal”). The Alter Rebbe now goes on to say that the word kideshanu also alludes to the sanctification a Jew achieves through Torah and mitzvot, sanctification implying a state of exaltation and separation from all worlds.

This is also the meaning of the blessings alluded to above: “Who has sanctified us by His commandments,” the verb kideshanu (“Who has sanctified us”) here meaning:

וְזֶהוּ שֶׁאוֹמְרִים: "אֲשֶׁר קִדְּשָׁנוּ בְּמִצְוֹתָיו" –

that He has elevated us to the heights of the supreme holiness, which is the holiness of the Holy One, blessed be He, Himself.

שֶׁהֶעֱלָנוּ לְמַעֲלַת קוֹדֶשׁ הָעֶלְיוֹן בָּרוּךְ־הוּא, שֶׁהִיא קְדוּשָּׁתוֹ שֶׁל הַקָּדוֹשׁ־בָּרוּךְ־הוּא בִּכְבוֹדוֹ וּבְעַצְמוֹ,

Kedushah (“holiness”) is a term indicating separateness, in that the Holy One, blessed be He, is apart from the worlds,

וּקְדוּשָּׁה – הִיא לְשׁוֹן הַבְדָּלָה, מַה שֶּׁהַקָּדוֹשׁ־בָּרוּךְ־הוּא הוּא מוּבְדָּל מֵהָעוֹלָמוֹת,

this being the quality of “encompassing all worlds,” being unable to clothe Himself within them.

וְהִיא בְּחִינַת סוֹבֵב כָּל עָלְמִין, מַה שֶּׁאֵינוֹ יָכוֹל לְהִתְלַבֵּשׁ בָּהֶן.

Because of the inability of created beings to absorb the extreme holiness of this transcendent level, G-d (as it were) cannot enclothe Himself within the worlds and therefore effects them in an encompassing manner. It is to this lofty level that Jews are elevated through their performance of mitzvot.

For through the union of the soul with, and its absorption into, the light of the Ein Sof, it attains the quality and the degree of holiness of the blessed Ein Sof Himself

כִּי עַל יְדֵי יִחוּד הַנֶּפֶשׁ וְהִתְכַּלְלוּתָהּ בְּאוֹר־אֵין־סוֹף בָּרוּךְ־הוּא, הֲרֵי הִיא בְּמַעֲלַת וּמַדְרֵגַת קְדוּשַּׁת אֵין־סוֹף בָּרוּךְ־הוּא מַמָּשׁ,

since it unites itself with Him and is integrated into Him, and they become truly one.

מֵאַחַר שֶׁמִּתְיַיחֶדֶת וּמִתְכַּלֶּלֶת בּוֹ יִתְבָּרֵךְ, וְהָיוּ לַאֲחָדִים מַמָּשׁ.

This is the meaning of the verse: “And you shall be holy unto Me, for I, the L-rd, am holy; the verse gives us the reason for the Jew’s sanctity, connecting it with G-d’s supreme holiness, which Jews can attain through Torah and mitzvot; and I have separated you from other peoples that you should be Mine.”14 Here we see that holiness implies separation, as mentioned earlier.

וְזֶהוּ שֶׁכָּתוּב: "וִהְיִיתֶם לִי קְדוֹשִׁים כִּי קָדוֹשׁ אֲנִי ה', וָאַבְדִּיל אֶתְכֶם מִן הָעַמִּים לִהְיוֹת לִי",

Another verse states: “You shall fulfill all My commandments and be holy unto your G-d: I am the L-rd your G-d….”15 The term “your G-d,” in the possessive form, recalls the relationship set up when a man betrothes a woman, whereby she becomes his wife.16

וְאוֹמֵר: "וַעֲשִׂיתֶם אֶת כָּל מִצְוֹתָי וִהְיִיתֶם קְדוֹשִׁים לֵאלֹהֵיכֶם אֲנִי ה' אֱלֹהֵיכֶם וְגוֹ'";

The meaning is that “through the fulfillment of the commandments, I become ‘your’ G-d,” in the same manner

פֵּירוּשׁ, כִּי עַל יְדֵי קִיּוּם הַמִּצְוֹת הֲרֵינִי אֱלוֹהַּ שֶׁלָּכֶם,

as G-d is called “the G-d of Abraham,” “the G-d of Isaac,” and so on,

כְּמוֹ "אֱלֹהֵי אַבְרָהָם אֱלֹהֵי יִצְחָק וְכוּ'",

called thus because the Patriarchs were on the level of a “vehicle” unto Him,

שֶׁנִּקְרָא כֵּן מִפְּנֵי שֶׁהָאָבוֹת הָיוּ בְּחִינַת מֶרְכָּבָה לוֹ יִתְבָּרֵךְ

The Patriarchs were totally dedicated to G-d and nullified before Him, like a vehicle (lit., “chariot”) which is totally nullified to its driver, possessing no independent will.

and they were nullified and absorbed in His light.

וּבְטֵלִים וְנִכְלָלִים בְּאוֹרוֹ.

So it is with the soul of every Jew at the time he is occupied with Torah and the commandments.

וְכָכָה הוּא בְּכָל נֶפֶשׁ מִיִּשְׂרָאֵל בִּשְׁעַת עֵסֶק הַתּוֹרָה וְהַמִּצְוֹת.

When a Jew occupies himself with Torah study and the performance of its commandments, he is totally nullified and absorbed in G-d’s light. The only difference between the Patriarchs and other Jews is that the Patriarchs were in this state constantly, while other Jews attain this level only at the abovementioned times.

Therefore, the Sages, of blessed memory, made it obligatory to rise and remain standing17 in the presence of anyone who is engaged in fulfilling a commandment, even if the latter is uncultured and illiterate. When such a person performs a mitzvah, such as bringing Bikkurim (the First Fruits) to the Beit Hamikdash, one must rise before him.

וְלָכֵן חִיְּיבוּ רַבּוֹתֵינוּ־זִכְרוֹנָם־לִבְרָכָה לָקוּם וְלַעֲמוֹד מִפְּנֵי כָּל עוֹסֵק בְּמִצְוָה, אַף אִם הוּא בּוּר וְעַם הָאָרֶץ,

This is because G-d dwells and clothes Himself in this man’s soul at such time.

וְהַיְינוּ, מִפְּנֵי ה' הַשּׁוֹכֵן וּמִתְלַבֵּשׁ בְּנַפְשׁוֹ בְּשָׁעָה זוֹ,

It is only that his soul is unconscious of this sanctity that resides within him at the time of his performance

רַק שֶׁאֵין נַפְשׁוֹ מַרְגֶּשֶׁת,

because of the barrier of the bodily grossness within which the soul dwells, which has of yet not been refined and which dims the eyes of the soul, preventing it from seeing Divine visions,

מִפְּנֵי מָסָךְ הַחוֹמֶר הַגּוּפָנִי, שֶׁלֹּא נִזְדַּכֵּךְ, וּמַחֲשִׁיךְ עֵינֵי הַנֶּפֶשׁ מֵרְאוֹת מַרְאוֹת אֱלֹהִים

as experienced by the Patriarchs and others of their stature, who “saw their world the spiritual World to Come during their lifetime.”

כְּמוֹ הָאָבוֹת וְכַיּוֹצֵא בָהֶן, שֶׁרָאוּ עוֹלָמָם בְּחַיֵּיהֶם.

These great tzaddikim were able in this world to see Divine visions normally seen only in the World to Come. This was so because their bodies, having been purified, did not conceal G-dliness. Truly, each and every Jew would be capable of witnessing such visions of holiness during the performance of a mitzvah were it not for the coarseness of his body.