Read about the Alter Rebbe here.
In principle, the spiritual service of circumcision is that of repentance.18 With regard to exile, our Sages teach that “if Israel repent, they will be immediately redeemed.”19 Repentance thus leads to the redemption (on a personal scale) of the Divine spark within each individual soul, and (on a cosmic scale) of the Shechinah, from their respective exiles. In spiritual terms, the act of circumcision likewise removes a veil of concealment and allows the innermost point of the heart to be revealed.
Now, in circumcision, there are two stages: milah (“excision”) and periah (“uncovering”),
וְהִנֵּה, בַּמִּילָה יֵשׁ שְׁנֵי בְּחִינוֹת: מִילָה וּפְרִיעָה,
[which remove respectively] the coarse foreskin and the thin membrane.
שֶׁהֵן עָרְלָה גַסָּה וּקְלִיפָּה דַקָּה.
With respect to the “foreskin” of the heart, which the Torah commands us similarly to circumcise, there are likewise coarse and subtle desires, corresponding to the two grades of skin.
וְכֵן בְּעָרְלַת הַלֵּב יֵשׁ גַּם כֵּן תַּאֲוֹת גַּסּוֹת וְדַקּוֹת –
[These two grades of worldly desire respectively require] milah and periah,
and “if one performed milah (‘circumcision’) without periah (‘uncovering’), it is as if he had not circumcised,”20
וּ"מָל וְלֹא פָרַע – כְּאִלּוּ לֹא מָל",
Just as this is the law with regard to actual circumcision, so, too, is it true when it comes to circumcising the desires of the heart: if a person removes only his coarse desires and does not proceed to remove the subtler ones as well, it is as if he had not circumcised his heart at all,
because, after all is said and done, the innermost point of the heart is still covered by a garment of thin sackcloth [of kelipah];
מִפְּנֵי שֶׁסּוֹף סוֹף עֲדַיִין נְקוּדַּת פְּנִימִית הַלֵּב הִיא מְכוּסָּה בִּלְבוּשׁ שַׂק דַּק,
it is in a state of exile and captivity.
בִּבְחִינַת גָּלוּת וְשִׁבְיָה.
There it will remain until the individual redeems it by performing a spiritual periah and removing his subtler desires as well.
Now, concerning the excision of the foreskin itself, it is written: “And you—yourselves—shall excise the foreskin of your heart.”
וְהִנֵּה, עַל מִילַת הָעָרְלָה מַמָּשׁ כְּתִיב "וּמַלְתֶּם אֵת עָרְלַת לְבַבְכֶם" אַתֶּם בְּעַצְמְכֶם.
Each and every Jew is able to remove this himself, for repentance tears down the veil with which his desires obscure the innermost point of his heart.
However, the removal of the thin membrane is a difficult matter for man,
אַךְ לְהָסִיר הַקְּלִיפָּה הַדַּקָּה, זֶהוּ דָּבָר הַקָּשֶׁה עַל הָאָדָם,
and of this, it is written that with the coming of Mashiach, “The L-rd your G‑d will circumcise your heart…, to love the L-rd your G‑d with all your heart and all your soul, for the sake of your life,”21
וְעַל זֶה נֶאֱמַר בְּבִיאַת הַמָּשִׁיחַ: "וּמָל ה' אֱלֹהֶיךָ אֶת לְבָבְךָ כוּ', לְאַהֲבָה אֶת ה' אֱלֹהֶיךָ בְּכָל לְבָבְךָ וּבְכָל נַפְשְׁךָ לְמַעַן חַיֶּיךָ",
because G‑d alone is literally your whole life.
כְּלוֹמַר – לְמַעַן כִּי ה' לְבַדּוֹ הוּא כָּל חַיֶּיךָ מַמָּשׁ,
In this state, the individual’s love of G‑d will not be a mere manifestation of his soul but a love that constitutes his very life. And just as a person does not regard his life as being something apart from himself, so, too, will this love not be sensed as a distinct entity but as an intrinsic component of himself.
That is why this love, the love that follows the Divine excision of the heart’s thin membrane, stems from the depth of the heart, from the truly innermost point, as mentioned above, and transcends the faculty of daat.
שֶׁלָּכֵן אַהֲבָה זוֹ הִיא מֵעוּמְקָא דְלִבָּא – מִנְּקוּדָּה פְּנִימִית מַמָּשׁ כַּנִּזְכָּר לְעֵיל, וּלְמַעְלָה מִבְּחִינַת הַדַּעַת.
Therefore, too, Mashiach will come when Israel in general are “caught unawares.”22
וְלָכֵן מָשִׁיחַ בָּא בְּהֶיסַּח הַדַּעַת לִכְלָלוּת יִשְׂרָאֵל,
[His coming] is the manifestation of the innermost point which is universal [to all Jews],
וְהִיא גִּילּוּי בְּחִינַת נְקוּדָּה פְּנִימִית הַכְּלָלִית,
and [likewise], the emergence of the universal Shechinah [of the entire community of Israel] from exile and captivity forever more.
וִיצִיאַת הַשְּׁכִינָה הַכְּלָלִית מֵהַגָּלוּת וְהַשִּׁבְיָה, לָעַד וּלְעוֹלְמֵי עוֹלָמִים.
Just as each individual’s Divine spark—his personal Shechinah, so to speak—is redeemed from captivity through means that transcend reason and daat, in such a manner, too, will the universal Shechinah, and with it the entire House of Israel, be redeemed.
Thus, the ultimate circumcision of the heart, and in its wake the ultimate manifestation of the love of G‑d, will take place when Mashiach comes. Nevertheless, it is possible even now to liberate one’s personal Shechinah—one’s Divine spark—at least on a temporary basis during the time of prayer.
20. Mishnah, Shabbat 137b; Yevamot 71b.
22.Sanhedrin 97a. The phrase hesach hadaat commonly implies that daat is absent because it has been forgotten; the Alter Rebbe’s interpretation makes daat absent because it has been transcended.