And this is the meaning of [the verse], “And your commandment is very wide.”
וְזֶהוּ "רְחָבָה מִצְוָתְךָ מְאֹד",
This refers to the precept of charity, which is a vessel of great volume, in which the radiance from the [infinite] Ein Sof-light may be invested,
הִיא מִצְוַת הַצְּדָקָה, שֶׁהִיא כְּלִי וְשֶׁטַח רָחָב מְאֹד, לְהִתְלַבֵּשׁ בָּהּ הֶאָרַת אוֹר־אֵין־סוֹף בָּרוּךְ־הוּא
In the future, this [light] will radiate without limit or end,
אֲשֶׁר יָאִיר לֶעָתִיד בִּבְחִינַת בְּלִי גְבוּל וְתַכְלִית
with a gratuitous [Divine] kindness elicited by this arousal from below—by the kindness and tzedakah initiated by man—which is called “the path of G-d.”
בְּחֶסֶד חִנָּם בְּ"אִתְעָרוּתָא דִלְתַתָּא" זוֹ, הַנִּקְרֵאת "דֶּרֶךְ ה'".
As mentioned above, even when this Divine revelation is granted in response to an arousal from below, it is still considered “gratuitous kindness,” for it is granted out of all proportion to man’s actions; man’s tzedakah is no more than a vessel which enables him to receive the benevolence of this Divine revelation.
And this is the meaning of the term “very [wide],” signifying limitlessness and endlessness: tzedakah acts as an infinitely wide vessel for receiving an infinite degree of G-dliness.
וְזֶהוּ לְשׁוֹן "מְאֹד", שֶׁהוּא בְּלִי גְבוּל וְתַכְלִית.
However, at the beginning of the verse quoted above, [it is written,] “To every tichlah (lit., “conclusion”), I have seen an end.”50
אֲבָל "לְכָל תִּכְלָה רָאִיתִי קֵץ",
The word tichlah is related to the term kalot hanefesh, the intense yearning—to the point of expiry—of the soul in Gan Eden,
"תִּכְלָה" הִיא מִלְּשׁוֹן "כְּלוֹת הַנֶּפֶשׁ" שֶׁבְּגַן עֵדֶן,
for it (i.e., the Divine light that is yearned for in Gan Eden) does have an end and a limit, and undergoes contraction, as mentioned above: this is the radiance of the finite light called memalei kol almin.
שֶׁהִיא בִּבְחִינַת "קֵץ" וְתַכְלִית וְצִמְצוּם כַּנִּזְכָּר לְעֵיל,
Likkutei Levi Yitzchak, authored by the father of the Rebbe, explains how “end,” “limit,” and “contraction” respectively refer to three kinds of illumination that radiate within Gan Eden. It also explains why the verse chooses to use the word “end” rather than “limit” or “contraction.”
As to the term “to every [kind of] tichlah,” when the verse is alluding only to the yearning of souls in Gan Eden,
וּ"לְכָל תִּכְלָה"
this is used because there are numerous levels and rungs of Gan Eden, one higher than the other, to the topmost of levels.
הוּא לְפִי שֶׁיֵּשׁ כַּמָּה וְכַמָּה מַעֲלוֹת וּמַדְרֵגוֹת גַּן עֵדֶן זֶה לְמַעְלָה מִזֶּה עַד רוּם הַמַּעֲלוֹת,
As is written in Likkutei Hashass of R. Yitzchak Luria, of blessed memory, in explanation of the teaching of our Sages, of blessed memory, “Torah scholars have no rest [in this world nor in the next],”51
כְּמוֹ שֶׁכָּתוּב בְּלִקּוּטֵי הַשַּׁ"ס מֵהָאֲרִיזַ"ל בְּפֵירוּשׁ מַאֲמַר רַבּוֹתֵינוּ־זִכְרוֹנָם־לִבְרָכָה: "תַּלְמִידֵי חֲכָמִים אֵין לָהֶם מְנוּחָה כוּ'",
because they are constantly rising from level to level in [their] grasp of the Torah, which has no end…—
שֶׁעוֹלִים תָּמִיד מִמַּדְרֵגָה לְמַדְרֵגָה בְּהַשָּׂגַת הַתּוֹרָה שֶׁאֵין לָהּ סוֹף כוּ',
until after the Resurrection, when they will have rest…, for that time will be “a day which is entirely Shabbat and rest.”52
עַד אַחַר הַתְּחִיָּה שֶׁיִּהְיֶה לָהֶם מְנוּחָה כוּ':
At that time, there will be revealed a radiance from G-d’s Essence that utterly transcends levels; elevation from level to level will thus be not only impossible but also unnecessary. At that time, mortal souls will finally find repose as they delight in the radiance of G-d’s Essence.
The Alter Rebbe now returns to the above-quoted verse, “Your commandment is very wide.” Having earlier explained that “Your commandment” (in the singular) refers to G-d’s own commandment, viz., tzedakah, he now goes on to explain the words “is very wide”: the mitzvah of tzedakah is a vessel so capacious that it can contain the revelation of G-d’s infinite light at the time of the Resurrection.