The Alter Rebbe distinguishes between yirah tata'ah (lower fear — fear of punishment and shame before God's omnipresence) and yirah ila'ah (higher awe — bitul and awe of God's infinite transcendence). He prescribes daily contemplation of God's presence as the practical method for awakening yirah.
שֶׁתְּהֵא בְּהִתְגַּלּוּת לִבּוֹ אוֹ מוֹחוֹ עַל כָּל פָּנִים. דְּהַיְינוּ, לְהִתְבּוֹנֵן בְּמַחֲשַׁבְתּוֹ עַל כָּל פָּנִים גְּדוּלַּת אֵין־סוֹף בָּרוּךְ־הוּא, וּמַלְכוּתוֹ אֲשֶׁר הִיא ״מַלְכוּת כָּל עוֹלָמִים״ – עֶלְיוֹנִים וְתַחְתּוֹנִים, וְאִיהוּ ״מְמַלֵּא כָּל עָלְמִין״ וְ״סוֹבֵב כָּל עָלְמִין״, וּכְמוֹ שֶׁכָּתוּב: ״הֲלֹא אֶת הַשָּׁמַיִם וְאֶת הָאָרֶץ אֲנִי מָלֵא״, וּמַנִּיחַ הָעֶלְיוֹנִים וְתַחְתּוֹנִים, וּמְיַיחֵד מַלְכוּתוֹ עַל עַמּוֹ יִשְׂרָאֵל בִּכְלָל, וְעָלָיו בִּפְרָט, כִּי חַיָּיב אָדָם לוֹמַר: ״בִּשְׁבִילִי נִבְרָא הָעוֹלָם״, וְהוּא גַם הוּא מְקַבֵּל עָלָיו מַלְכוּתוֹ, לִהְיוֹת מֶלֶךְ עָלָיו, וּלְעָבְדוֹ וְלַעֲשׂוֹת רְצוֹנוֹ בְּכָל מִינֵי עֲבוֹדַת עָבֶד. 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.
By this is meant that, although fear is the root of “turn away from evil” and love—of “do good,” nevertheless it is not sufficient to awaken the love alone to do good, but one must at least first arouse the innate fear which lies hidden in the heart of every Jew not to rebel against the Supreme King of kings, the Holy One, blessed is He, as has been stated above so that this [fear] shall manifest itself in his heart or, at least, his mind. This means that he should at least contemplate in his thought on the greatness of the En Sof, blessed is He, and on His Kingship, which extends to all worlds, both higher and lower, and that “He fills all worlds and encompasses all worlds,” as is written, “Do I not fill heaven and earth?” Yet He leaves both the higher and lower [worlds] and uniquely bestows His Kingdom upon His people Israel in general, and upon him in particular, as, indeed, a man is obliged to say, “For my sake was the world created.” And on his part, he accepts His Kingdom upon himself, that He be King over him, to serve Him and do His will in all kinds of servile work. “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.