The emperor Hadrian asked Rabbi Yehoshua. He said to him: Is there a Master over the world? He said to him: And would the world be ownerless? He said to him: And who created heaven and earth? He said to him: The Holy One, blessed be He, as it is said, "In the beginning He created" and so on (Genesis 1:1). He said to him: Then why does He not reveal Himself twice a year, so that creatures may see and their dread of Him be upon them? He said to him: Because the world cannot endure His radiance, as it is said, "For no human can see Me and live" (Exodus 33:20). He said to him: If you do not show me, I will not believe you. At midday he stood him facing the sun and said to him: Gaze at the sun and you will see Him. He said to him: And who can gaze at the sun? He said to him: Will your ears not hear what your mouth is saying? If the sun, which is but one of a thousand thousands and myriad myriads of servants who serve before Him, and no creature is able to gaze upon it, then the Holy One, blessed be He, whose radiance fills the world, how much more so. And when does He reveal His glory? When idols will perish from the world, as it is said, "And the idols shall utterly pass away" (Isaiah 2:18), and afterward, "And the LORD alone shall be exalted" (Isaiah 2:11), and it says, "And the glory of the LORD shall be revealed" and so on (Isaiah 40:5). The soul does not leave the body until it sees the face of the Divine Presence, as it is said, "For no human can see Me and live" (Exodus 33:20). "Behold, there is a place by Me" (Exodus 33:21).
Hadrian, Rabbi Yehoshua, and the Light No Eye Can Bear
Yalkut Shimoni on Torah 396:3
שָׁאַל אַנְדְּרִיָּנוּס קֵיסָר לְרַבִּי יְהוֹשֻׁעַ. אָמַר לוֹ. יֵשׁ אָדוֹן לָעוֹלָם. אֲמַר לֵיהּ. וְכִי עוֹלָם שֶׁל הֶפְקֵר הוּא. אָמַר לוֹ. וּמִי בָּרָא שָׁמַיִם וָאָרֶץ. אָמַר לוֹ. הַקָּדוֹשׁ בָּרוּךְ הוּא, שֶׁנֶּאֱמַר "בְּרֵאשִׁית בָּרָא וְגוֹ'. אָמַר לוֹ, וְלָמָּה אֵינוֹ נִגְלֶה שְׁתֵּי פְּעָמִים בַּשָּׁנָה, כְּדֵי שֶׁיִּרְאוּ הַבְּרִיּוֹת וּתְהֵא אֵימָתוֹ עֲלֵיהֶן. אָמַר לוֹ. לְפִי שֶׁאֵין הָעוֹלָם יָכוֹל לַעֲמֹד בְּזִיווֹ, שֶׁנֶּאֱמַר כִּי לֹא יִרְאַנִי הָאָדָם וָחָי. אָמַר לוֹ. אִם אֵינְךָ מַרְאֶה, אֵינִי מַאֲמִינְךָ. לַחֲצִי הַיּוֹם הֶעֱמִידוֹ כְּנֶגֶד הַשֶּׁמֶשׁ. אָמַר לוֹ. הִסְתַּכֵּל בַּשֶּׁמֶשׁ וְאַתָּה רוֹאֵהוּ. אָמַר לוֹ. וּמִי יָכוֹל לְהִסְתַּכֵּל בַּשֶּׁמֶשׁ. אָמַר לוֹ. וְלֹא יִשְׁמְעוּ אָזְנֶיךָ מַה שֶּׁפִּיךָ מְדַבֵּר, וּמַה הַשֶּׁמֶשׁ, שֶׁהוּא אֶחָד מֵאֶלֶף אֲלָפִים וְרִבּוֹא רִבְוָן מִמְּשַׁמְּשִׁין שֶׁמְּשַׁמְּשִׁין לְפָנָיו, אֵין כָּל בְּרִיָּה יְכוֹלָה לְהִסְתַּכֵּל בּוֹ, הַקָּדוֹשׁ בָּרוּךְ הוּא, שֶׁזִּיווֹ מָלֵא עוֹלָם, עַל אַחַת כַּמָּה וְכַמָּה, וְאֵימָתַי הוּא מְגַלֶּה כְבוֹדוֹ, כְּשֶׁיֹּאבְדוּ אֱלִילִים מִן הָעוֹלָם, שֶׁנֶּאֱמַר (ישעיה ב, יח) "וְהָאֱלִילִים כָּלִיל יַחֲלֹף", וְאַחַר כָּךְ (שם, יא) "וְנִשְׂגַּב ה' לְבַדּוֹ", וְאוֹמֵר (שם מ, ה) "וְנִגְלָה כְּבוֹד ה'" וְגוֹ'. אֵין הַנֶּפֶשׁ יוֹצְאָה מִן הַגּוּף עַד שֶׁתִּרְאֶה פְּנֵי הַשְּׁכִינָה, שֶׁנֶּאֱמַר כִּי לֹא יִרְאַנִי הָאָדָם וָחָי. הִנֵּה מָקוֹם אִתִּי.