To explain the above:וְהָעִנְיָן הוּא,
A Jew’s willingness to sacrifice his life for his faithדְּזֶה שֶׁהָאֱמוּנָה דְּיִשְׂרָאֵל הִיא בְּאֹפֶן שֶׁהוּא מוֹסֵר נַפְשׁוֹ עַל זֶה,
stems (primarily) from the faith rooted in the essence of his soul.הוּא (בְּעִקָּר) בְּהָאֱמוּנָה שֶׁמִּצַּד עֶצֶם הַנְּשָׁמָה.
For the faith that stems from sight (“its mazal perceives”) does not motivate such a commitment.דְּהָאֱמוּנָה מִצַּד זֶה שֶׁהוּא רוֹאֶה (מַזְלֵיהּ חָזֵי),
Although the faith inspired by this perception is also very forceful,הֲגַם שֶׁהִיא בְּתֹקֶף גָּדוֹל
[for the impression created by sight is extremely powerful],[כַּיָּדוּעַ דְּהַהִתְאַמְּתוּת שֶׁמִּצַּד הָרְאִיָּה הִיא הִתְאַמְּתוּת גְּדוֹלָה בְּיוֹתֵר],
Indeed, because sight creates such a powerful impression, “a witness may not serve as a judge.”1 This law emphasizes how deeply sight affects one’s thinking processes. As our Sages state, once a person has seen a misdeed committed, he will no longer be able to think of a factor that will exonerate the defendant. If he simply hears testimony from two trustworthy witnesses, he also knows with assurance that the misdeed was committed. Nevertheless, the effect on his thinking processes will not be as great, and he will be able to think of redeeming factors that might exonerate the defendant. If, however, he saw the misdeed committed, such thoughts will not arise.
nevertheless, since this faith comes from an external factorמִכָּל מָקוֹם, כֵּיוָן שֶׁהָאֱמוּנָה שֶׁלּוֹ הִיא מִצַּד סִבָּה
(i.e., the soul’s perception),(מִצַּד זֶה שֶׁרוֹאֶה)
and is not connected with the essence of its being,וְאֵינָהּ קְשׁוּרָה עִם עֶצֶם מְצִיאוּתוֹ,
it does not necessitate mesirus nefesh.אֵינוֹ מֻכְרָח שֶׁיִּמְסֹר נַפְשׁוֹ עַל זֶה,
Why will a Jew give up his life for his faith?וְזֶה שֶׁהָאֱמוּנָה דְּיִשְׂרָאֵל הִיא בְּאֹפֶן שֶׁהוּא מוֹסֵר נַפְשׁוֹ עַל זֶה
Because faith in G‑d is the very essence of his being.הוּא מִפְּנֵי שֶׁהָאֱמוּנָה בֵּאלֹקוּת הִיא הָעֶצֶם שֶׁלּוֹ,
Ordinarily, a person does not give up his life for an ideal. No matter how deeply that ideal will affect him, the ideal is still something outside of him, and he will consider his own life more precious.
True, there may be some refined individuals who are prepared to sacrifice their lives for what they believe in. Even in their instance, however, it is not because their essence has been touched, but rather because they are deeply involved with their beliefs intellectually and emotionally. Jews, however, do not give up their lives for G‑d due to the depth of their understanding and/or emotional involvement, but because of their essential bond with Him. For that reason, simple people, and even those who profess to be non-believers, have sacrificed their lives in sanctification of G‑d’s name.
And therefore, it is impossible for him to deny G‑d, Heaven forbid.וְלָכֵן אִי אֶפְשָׁר כְּלָל שֶׁיִּכְפֹּר חַס וְשָׁלוֹם.
As the Alter Rebbe would say:2 “No Jew can – and no Jew will – allow himself to be cut off from G‑d.”
Based on the above, we can explain the statement in the maamar VeKibeil HaYehudim that Moshe’s function as a “shepherd of faith”וְעַל פִּי זֶה יֵשׁ לְבָאֵר מַה שֶּׁכָּתוּב בְּהַמַּאֲמָר דְּזֶה שֶׁמֹּשֶׁה הוּא רַעֲיָא מְהֵימְנָא
(that he sustains and nurtures the faith of the Jews)(שֶׁהוּא זָן וּמְפַרְנֵס אֶת הָאֱמוּנָה)
applies also to the “shepherds of Israel” (“the extensions of Moshe”) in every generation,הוּא גַּם בְּנוֹגֵעַ לְרוֹעֵי יִשְׂרָאֵל שֶׁבְּכָל דּוֹר (אִתְפַּשְּׁטוּתָא דְּמֹשֶׁה שֶׁבְּכָל דָּרָא)
for they strengthen the faith of the Jewish people,שֶׁהֵם מְחַזְּקִים אֶת הָאֱמוּנָה דְּיִשְׂרָאֵל
inspiring them to manifest self-sacrifice for the sake of the observance of the Torah and its mitzvos.שֶׁיַּעַמְדוּ בִּמְסִירוּת נֶפֶשׁ בְּקִיּוּם הַתּוֹרָה וּמִצְוֹת.
On this basis, we can understand the meaning of the term “shepherd of faith,” that Moshe and the subsequent “shepherds” of the Jewish people nurture the faith of the Jewish people. By arousing the essence of the Jews, they elevate the power of their faith. This, in turn, makes mesirus nefesh, “self-sacrifice,” a natural response.
On the surface, the above statement is problematic.דְּלְכִאוֹרָה,
(In several sources3 and in the maamar VeKibeil HaYehudim itself4) it is explained that Moshe’s efforts to sustain and nurture the faith of the Jewish people זֶה שֶׁמֹּשֶׁה זָן וּמְפַרְנֵס אֶת הָאֱמוּנָה הוּא (כַּמְּבֹאָר בְּכַמָּה מְקוֹמוֹת וְגַם בְּמַאֲמָר זֶה עַצְמוֹ)
is accomplished by infusing them with the knowledge – and the internalized awareness – of G‑d.עַל יְדֵי שֶׁמַּשְׁפִּיעַ לְיִשְׂרָאֵל דַּעַת בֵּאלֹקוּת
This enables the faith of the Jewish people to be internalized.שֶׁעַל יְדֵי זֶה בָּאָה הָאֱמוּנָה בִּפְנִימִיּוּת,
However, (in the maamar VeKibeil HaYehudim,) it is also explained that the shepherds of Israel in every generation strengthen the faith of the Jewish people,וְזֶה שֶׁרוֹעֵי יִשְׂרָאֵל שֶׁבְּכָל דּוֹר מְחַזְּקִים הָאֱמוּנָה (הַמְּבֹאָר בְּמַאֲמָר זֶה)
inspiring them to self-sacrifice.הוּא שֶׁהָאֱמוּנָה דְּיִשְׂרָאֵל תִּהְיֶה בְּאֹפֶן דִּמְסִירוּת נֶפֶשׁ.
In contrast to Tanya, loc. cit., which states that “sparks from the soul of Moshe Rabbeinu descend... to impart knowledge to the people.”
The Rebbe is highlighting the uniqueness of the interpretation of the concept of “the extensions of Moshe” found in the maamar entitled VeKibeil HaYehudim. In Tanya, loc. cit., the Alter Rebbe explains that the function of “the extensions of Moshe” resembles that of Moshe himself – enabling the Jewish people to internalize their faith through knowledge. In the maamar entitled VeKibeil HaYehudim, by contrast, the Rebbe Rayatz states that the contribution of “the extensions of Moshe” is to inspire mesirus nefesh, self-sacrifice. As explained above, this does not come about through imparting knowledge, but rather by bringing to the fore the connection to G‑d shared by the essence of the soul, a bond that transcends knowledge.
Based on the above, this difficulty can be resolved as follows:וְעַל פִּי הַנִּזְכָּר לְעֵיל יֵשׁ לוֹמַר,
The primary activity of a “shepherd of faith” is to sustain and nurture faith itself,שֶׁעִיקַּר הָעִנְיָן דְּרַעֲיָא מְהֵימְנָא הוּא זֶה שֶׁהוּא זָן וּמְפַרְנֵס אֶת הָאֱמוּנָה עַצְמָהּ,
i.e., to lift our faith above the influence of our revealed powersשֶׁהָאֱמוּנָה תִּהְיֶה לֹא רַק כְּמוֹ שֶׁהִיא מִצַּד הַגִּלּוּיִים
(the peak of this being the soul’s perception of G‑dliness),(מִצַּד זֶה שֶׁהַנְּשָׁמָה שֶׁלְּמַעְלָה רוֹאָה אֱלֹקוּת)
rather, to have our faith reflect the essence of the soul.אֶלָּא מִצַּד עֶצֶם הַנְּשָׁמָה.
The expression “shepherd of faith” implies that faith itself is nourished and brought to a higher level. Generally, it is explained that the influence of Moshe – and the extensions of Moshe in every generation – enables faith to be internalized within one’s powers of thought. According to that interpretation, the person’s spiritual potential is being nourished, but faith itself is not. According to the interpretation here, Moshe awakens the essence of the soul within the Jewish people and, as a result, faith itself is being elevated to a level that reflects the essence of the soul.
In this context, Moshe’s achievements in internalizing faithוְזֶה שֶׁמֹּשֶׁה מַמְשִׁיךְ אֶת הָאֱמוּנָה בִּפְנִימִיּוּת
(bringing it within the realm of knowledge and comprehension)(בְּדַעַת וְהַשָּׂגָה)
is an outgrowth of his efforts to sustain and nurture faith itself,הוּא תּוֹצָאָה מִזֶּה שֶׁהוּא זָן וּמְפַרְנֵס אֶת הָאֱמוּנָה עַצְמָהּ
(drawing down and revealing the dimension of faith that stems from the essence of the soul),(הַמְשָׁכַת וְגִלּוּי הָאֱמוּנָה כְּמוֹ שֶׁהִיא מִצַּד עֶצֶם הַנְּשָׁמָה).
as explained above (sec. 5).וְכַנַּ"ל (סְעִיף ה),
For the possibility for faith to be internalized (and drawn into the realm of knowledge)דְּהַמְשָׁכַת הָאֱמוּנָה בִּפְנִימִיּוּת (בְּדַעַת)
comes from the revelation of the essential bond between G‑d and the essence of the soul.הוּא עַל יְדֵי גִּלּוּי הַהִתְקַשְּׁרוּת עַצְמִית דְּעֶצֶם הַנְּשָׁמָה.
Faith represents a potential that transcends limitations. A person’s conscious powers of intellect and emotion, by contrast, are limited potentials. Therefore, faith usually functions as an encompassing light. Internalizing faith thus represents a fusion of opposites, and such fusion is only possible because of the revelation of the soul’s essence.
Based on the above,וְעַל פִּי זֶה יֵשׁ לוֹמַר,
it can be explained that in the generations in which actual mesirus nefesh was required and people indeed risked and gave up their lives,דִּבְזֶה שֶׁבְּהַדּוֹרוֹת שֶׁהֻצְרְכוּ לִמְסִירוּת נֶפֶשׁ בְּפֹעַל
the shepherds of Israel (“the extensions of Moshe”) who strengthened the faith of the Jewish people,חִזְּקוּ רוֹעֵי יִשְׂרָאֵל (אִתְפַּשְּׁטוּתָא דְּמֹשֶׁה) אֶת הָאֱמוּנָה דְּיִשְׂרָאֵל
inspiring them to self-sacrifice,שֶׁתִּהְיֶה בִּמְסִירוּת נֶפֶשׁ,
expressed the qualities of a shepherd of faith (in this context) to a greater extent than did Moshe himself.נִתְגַּלָּה הָעִנְיָן דְּרַעֲיָא מְהֵימְנָא (בְּעִנְיָן זֶה) עוֹד יוֹתֵר מִבְּמֹשֶׁה עַצְמוֹ,
Until now, the maamar has explained two effects of the expression of the essence of the soul brought about by Moshe and the subsequent shepherds of the Jewish people: a) self-sacrifice; and b) the internalization of faith to the extent that it elevates one’s conscious powers. Self-sacrifice was not required of the Jewish people in Moshe’s era. On the contrary, during their journey through the desert all their needs were met. What was Moshe’s contribution? He elevated his people until they became a dor dei’ah, “a generation of knowledge,” i.e., he imbued them with knowledge that enabled them to internalize faith. Such knowledge can only be attained through the influence of the essence of the soul.
Nevertheless, self-sacrifice is a more revealing expression of the soul’s essence than such knowledge. Knowledge is, after all, only a revealed quality, something removed from the essence of a person’s soul. By sacrificing his life for his faith, the person shows that his faith lies at the essence of his being – it reflects who he is.
For the expression and the revelation of the dimension of faith which stems from the essence of the soulכִּי הַמְשָׁכַת וְגִלּוּי הָאֱמוּנָה כְּמוֹ שֶׁהִיא מִצַּד עֶצֶם הַנְּשָׁמָה
[which is inspired by Moshe and “the extension of Moshe in every generation”][שֶׁעַל יְדֵי מֹשֶׁה וְאִתְפַּשְּׁטוּתָא דִּילֵיהּ שֶׁבְּכָל דָּרָא],
is primarily manifestעִיקַּר הִתְגַּלּוּתָהּ
in actual self-sacrifice.הוּא מְסִירוּת נֶפֶשׁ בְּפֹעַל.
Moshe did not achieve this in his generation. It was unnecessary for him to do so because he led the Jewish people on their journey through the desert when they were protected by G‑d’s revealed miracles.5 In subsequent generations, when the Jewish people were threatened by non-Jews, it was the “extensions of Moshe” who aroused the essence of the souls of the Jewish people and spurred them to mesirus nefesh.

Summary

A Jew’s willingness to sacrifice his life for his faith stems primarily from the faith rooted in the essence of his soul. Why will a Jew give up his life for his faith? Because faith in G‑d is the very essence of his being.
Similarly, the “shepherds of Israel,” “the extensions of Moshe” in every generation, strengthen the faith of the Jewish people, inspiring them to manifest self-sacrifice for the sake of the observance of the Torah and its mitzvos by revealing the essence of their souls.
In other sources, it is explained that Moshe serves as “a shepherd of faith” by imparting knowledge to the Jewish people. There is no contradiction between the two concepts. The primary activity of a “shepherd of faith” is to sustain and nurture faith itself, i.e., to lift our faith above the influence of our revealed powers by revealing the essence of the soul. Moshe’s achievements in internalizing faith – bringing it within the realm of knowledge and comprehension – is an outgrowth of his efforts to sustain and nurture faith itself through the revelation of the essence of the soul. For the possibility for faith to be internalized comes from the revelation of the essential bond between G‑d and the essence of the soul.
The shepherds of Israel (“the extensions of Moshe”) who strengthened the faith of the Jewish people, inspiring them to self-sacrifice, expressed the qualities of a shepherd of faith to a greater extent than did Moshe himself. For the revelation of the dimension of faith which stems from the essence of the soul, inspired by “the extensions of Moshe in every generation,” is primarily manifest through actual self-sacrifice.