The Tanya teaches that actions such as mitzvot and physical objects can draw divine awareness into everyday life. In this chapter, mitzvah observance is framed as channeling fear of Heaven into lived experience, which fits the mezuzah as a home-facing reminder.
וְהִנֵּה ה׳ נִצָּב עָלָיו, וּ״מְלֹא כָל הָאָרֶץ כְּבוֹדוֹ״, וּמַבִּיט עָלָיו, וּבוֹחֵן כְּלָיוֹת וָלֵב אִם עוֹבְדוֹ כָּרָאוּי. וְעַל כֵּן צָרִיךְ לַעֲבוֹד לְפָנָיו בְּאֵימָה וּבְיִרְאָה, כְּעוֹמֵד לִפְנֵי הַמֶּלֶךְ. וְיַעֲמִיק בְּמַחֲשָׁבָה זוֹ וְיַאֲרִיךְ בָּהּ כְּפִי יְכוֹלֶת הַשָּׂגַת מוֹחוֹ וּמַחֲשַׁבְתּוֹ, וּכְפִי הַפְּנַאי שֶׁלּוֹ, לִפְנֵי עֵסֶק הַתּוֹרָה, אוֹ הַמִּצְוָה, כְּמוֹ לִפְנֵי לְבִישַׁת טַלִּית וּתְפִילִּין. וְגַם יִתְבּוֹנֵן, אֵיךְ שֶׁאוֹר־אֵין־סוֹף בָּרוּךְ־הוּא, הַ״סּוֹבֵב כָּל עָלְמִין״ וּ״מְמַלֵּא כָּל עָלְמִין״, הוּא רָצוֹן הָעֶלְיוֹן, הוּא מְלוּבָּשׁ בְּאוֹתִיּוֹת וְחָכְמַת הַתּוֹרָה, אוֹ בְּצִיצִית וּתְפִלִּין אֵלּוּ, וּבִקְרִיאָתוֹ אוֹ בִּלְבִישָׁתוֹ הוּא מַמְשִׁיךְ אוֹרוֹ יִתְבָּרֵךְ עָלָיו, דְּהַיְינוּ עַל ״חֵלֶק אֱלוֹהַּ מִמַּעַל״ שֶׁבְּתוֹךְ גּוּפוֹ, לִיכָּלֵל וְלִיבָּטֵל בְּאוֹרוֹ יִתְבָּרֵךְ.
“And, behold, G–d stands over him,” and “The whole world is full of His glory,” and He looks upon him and “Searches his reins and heart” [to see] if he is serving Him as is fitting. Therefore he must serve in His presence with awe and fear like one standing before the king. One must meditate profoundly and at length on this thought according to the capacity of apprehension of his brain and thought and according to the time available to him, before he occupies himself with Torah or a commandment, such as prior to putting on his tallit or tefillin. He should also reflect how the light of the En Sof, blessed is He, which encompasses all worlds and pervades all worlds, which is identical with the Supernal Will, is clothed in the letters and wisdom of the Torah and in the tzitzit and the tefillin, and through his study or donning these latter he draws over himself His light, blessed be He, that is, over “the portion of G–dliness from above” which is within his body, that it may be absorbed and nullified in His light, blessed be He.