(1) You are children of your God. You shall not gash yourselves or shave the front of your heads because of the dead. (2) For you are a people consecrated to your God ה׳: your God ה׳ chose you from among all other peoples on earth to be a treasured people.
Reish Lakish said to Rabbi Yoḥanan: I should read here the verse: “You shall not cut yourselves [titgodedu]” (Deuteronomy 14:1), which is interpreted as meaning: Do not become numerous factions [agudot]. In other words, the Jewish people should be united, rather than divided into disparate groups that act in different ways. Before analyzing this issue, the Gemara asks: This verse: “You shall not cut yourselves,” is required for the matter itself, as the Merciful One is saying: Do not cut yourselves over the dead. How is the halakha concerning factions derived from this apparently straightforward verse?
The Gemara answers: If so, that the verse comes to teach only about the practices of mourning, let the verse state only: You shall not cut. What is the meaning of: “You shall not cut yourselves”? Learn from this that it comes for this purpose as well, to teach the prohibition against splitting into factions. The Gemara asks: But in that case, one can say that the entire verse comes for this purpose and does not refer to cutting for the dead at all. The Gemara answers: If so, let the verse state: Lo tagodu, rather than lo titgodedu, both of which mean: You shall not cut. What is the meaning of: “Lo titgodedu”? Conclude two conclusions from it: Both the simple prohibition against making cuts for the dead and the matter of dividing into factions.
כִּי אֵין זֶה דֶּרֶךְ הָעֲנָוָה הָאֲמִתִּיִּית שֶׁיַּחֲזִיק אֶת עַצְמוֹ לְרָשָׁע גָּמוּר ח"ו, וּלְהַקְטִין מַעֲלַת נַפְשׁוֹ הַקְּדוֹשָׁה רַק, אַדְּרַבָּא, צָרִיךְ לֵידַע וּלְהַאֲמִין שֶׁנַּפְשׁוֹ בְּשָׁרְשָׁהּ הִיא גְּדוֹלָה וִיקָרָה וְגָבֹהַּ מְאֹד מְאֹד וְאַלְפֵי אֲלָפִים וְרִבֵּי רִבְבוֹת עוֹלָמוֹת בְּלִי שִׁעוּר תְּלוּיִים בָּהּ וּכְמוֹ שֶׁאָמַר רַבֵּנוּ זַ"ל שֶׁאִם הָיוּ מְהַפְּכִין אֶת הָאָדָם הָיוּ רוֹאִין שֶׁבְּכָל גִּיד וְגִיד מִגִּידֵי הָאָדָם תְּלוּיִים אַלְפֵי אֲלָפִים וְרִבֵּי רִבְבוֹת עוֹלָמוֹת וְכַמְבֹאָר בִּשְׁאָר סְפָרִים מִגֹּדֶל מַעֲלַת הָאָדָם שֶׁהוּא בְּחִינַת צֶלֶם אֱלֹקִים וַאֲפִלּוּ נֶפֶשׁ הַפָּחוֹת שֶׁבַּפְּחוּתִים שֶׁל יִשְׂרָאֵל גַּם כֵּן גָּבֹהַּ מְאֹד מְאֹד...
This is because the path of authentic humility is not to consider oneself a completely wicked person, and to belittle the value of one’s holy soul, but on the contrary, to know and believe that one’s soul at its source is extremely great, precious and exalted, and that ‘ many countless thousands and myriads of worlds without measure depend upon it. As Rabbeinu z"l said, if one could turn a human being inside out, one would see how thousands and myriads of worlds are dependent upon each and every part of the human body, as the greatness of the human being, representing the image of God, is explained in other texts. And even the lowliest feeling Jewish soul is also a child of the Divine as we are all created in the Divine image.
טוֹב מְאֹד מִי שֶׁיָּכוֹל לִשְׁפֹּךְ שִׂיחוֹ לִפְנֵי הַשֵּׁם יִתְבָּרַךְ בְּרַחֲמִים וְתַחֲנוּנִים כְּבֵן הַמִּתְחַטֵּא לִפְנֵי אָבִיו. כִּי הֲלֹא הַשֵּׁם יִתְבָּרַךְ כְּבָר קְרָאָנוּ בָּנִים כְּמוֹ שֶׁכָּתוּב: "בָּנִים אַתֶּם לַה' אֱלֹקֵיכֶם" (דְּבָרִים י"ד). עַל־כֵּן טוֹב מְאֹד לְפָרֵשׁ שִׂיחָתוֹ וְצַעֲרוֹ לְפָנָיו יִתְבָּרַךְ, כְּבֵן שֶׁקּוֹבֵל לִפְנֵי אָבִיו בִּתְנוּעוֹת שֶׁל חֵן וְרַחֲמִים (שֶׁקּוֹרִין פְּיֶעשְׁטְשֶׁין).
It is very good to pour out your thoughts before God (cf. Psalms 142:3), like a child pleading before their parent(Ta'anit 19a). God calls us God's children, as it is written, “You are children to the Lord your God” (Deuteronomy 14:1). Therefore, it is good to express your thoughts and troubles to God, like a child complaining and pestering their parent (Alim LeTerufah #254).
In both cases the Jew is summoned to be cognizant of the sacred soul that permeates one’s fellow person. In the case of death, although it is normal and proper to weep and mourn the loss of a dear one, one curtails any extreme expression of loss knowing that the soul is everlasting. The soul of the living and the one who has departed remain permanently connected on a ‘soul’ level; that immeasurable bond can never be terminated. When we place less emphasis on the physical we would naturally be more inclined to love others with greater affection and closeness. In the case of the prohibition of forming factions, we err by making divisions often as a result of being oblivious to the holy neshamah inherent in our fellow person. It is only the physical dimension of our existence that differs person to person. Indeed, when we focus on the spiritual side of things we gain a growing appreciation of the similarities between people and the substantial common ground - and this is the key to attaining unity. We are obliged to recognize that every soul of every member of Klal Yisrael is from the same root; we are all part of one spiritual entity.