However, the letters exist on planes of “matter” and “form,” which are also referred to as their “internal” aspect (i.e., the “form,” which is their “soul”) and their “external” aspect (i.e., the “matter,” which is their “body”).
אַךְ הָאוֹתִיּוֹת הֵן בִּבְחִינַת חוֹמֶר וְצוּרָה, הַנִּקְרָא פְּנִימִית וְחִיצוֹנִית,
Although their source is the primordial stage of the intellect and the will of the soul, for as soon as the soul desires to speak these letters are formed, as explained above,
כִּי הֲגַם שֶׁמְּקוֹרָן הוּא מִקַּדְמוּת הַשֵּׂכֶל וּרְצוֹן הַנֶּפֶשׁ,
this is but the “form” of the differentiation in the pronunciation of the twenty-two letters.
זוֹ הִיא בְּחִינַת צוּרַת שִׁינּוּי הַמִּבְטָא שֶׁבְּכ"ב אוֹתִיּוֹת,
The “matter” and “body” of their formation, however, i.e., the aspect of their “externality,” is the breath issuing from the heart.
אֲבָל בְּחִינַת הַחוֹמֶר וְגוּף הִתְהַוּוּתָן, וְהוּא בְּחִינַת חִיצוֹנִיּוּתָן, הוּא הַהֶבֶל הַיּוֹצֵא מֵהַלֵּב,
From this breath is formed a simple sound which proceeds from the throat,
שֶׁמִּמֶּנּוּ מִתְהַוֶּה קוֹל פָּשׁוּט הַיּוֹצֵא מֵהַגָּרוֹן,
and which is then divided into the twenty-two kinds of enunciation and expression of the twenty-two letters,
וְאַחַר כָּךְ נֶחְלָק לְכ"ב הֲבָרוֹת, וּבִיטּוּי כ"ב אוֹתִיּוֹת
[these divisions taking place] through the five known organs of speech: alef, chet, hey, and ayin18 through the throat;
בְּה' מוֹצָאוֹת הַיְדוּעוֹת: אחה"ע מֵהַגָּרוֹן,
gimmel, yud, kaf, and kuf through the palate, and so on; e.g., beit, vav, mem, and pey from the lips, and so on;
גיכ"ק מֵהַחֵיךְ כוּ'.
while the breath itself, which has its own sound independent of the letter being spoken, is uttered by the letter hey19—“the light letter…,” inasmuch as it lacks the substance of a complete letter,
וּמִבְטָא הַהֶבֶל הוּא אוֹת ה' "אָתָא קַלִּילָא כוּ'",
which is the source of the “matter” and “body” of the letters before their division into twenty-two.
וְהוּא מְקוֹר הַחוֹמֶר וְגוּף הָאוֹתִיּוֹת טֶרֶם הִתְחַלְּקוּתָן לְכ"ב,
The hey is thus the source of each letter’s “body.”
And that is why our Sages, of blessed memory, said that “this world was created by the hey”: it was created by the external aspect, or “body,” of the supernal letters whose source is the hey of the Divine Name.
וְלָכֵן אָמְרוּ רַבּוֹתֵינוּ־זִכְרוֹנָם־לִבְרָכָה, שֶׁ"עוֹלָם הַזֶּה נִבְרָא בְּה'":
Until this point, the Alter Rebbe has explained the Talmudic teaching that the World to Come was created by the letter yud: the sefirah of chochmah, which this letter represents, is the spiritual source of Gan Eden, which is in the World to Come.
However, according to the above, since the letters of the supernal creative speech derive from chochmah, it would seem that this world, which was also created by the letters of Divine speech, was likewise created from the letter yud that represents chochmah. Why, then, do our Sages teach that only the World to Come was created from the letter yud, while this world was created from the letter hey?
The Alter Rebbe therefore now goes on to explain that the letters of speech are composed of “matter” and “form” the “body” and “soul” (or: the external and internal aspects) of the letters. While the “form” of the letters does indeed derive from chochmah, the “matter” of the letters of speech merely derives from the heart.
So, too, Above: the internal aspect of the letters derives from chochmah; from this aspect are created the higher spiritual beings which are able to apprehend G-dliness. However, the external aspect of the supernal letters of speech derives from the “breath,” the hey of the Divine Name. It is from this lesser level that this physical world was created.
In the words of the Alter Rebbe: