Rabbi Chiyya bar Abba said: it was a coronation day [yom genusya], and all the kings were coming and crowning him, for he was a world-ruler, and Moses and Aaron were standing at the entrance of the palace. They entered to Pharaoh and said to him, "Two old men are standing at the entrance of your palace." He said to them, "Do they have crowns in their hands?" They said to him, "No." He said to them, "Let them enter last." They entered to Pharaoh. He said to them, "What do you seek?" They said to him, "The God of the Hebrews has sent me to you" (Exodus 7:16) — "Send out My people that they may celebrate a feast to Me in the wilderness." He said to them, "Who is the LORD that I should heed His voice" (Exodus 5:2), and He did not even know how to send me a crown of His own, but came to me only with words? "Who is the LORD that I should heed His voice?" Rabbi Levi said: at that hour he brought out the register [diftera] of deities and read out, "the god of Edom, Moab, and Sidon," and said to them, "Behold, I have read and I do not find what you speak of." Rabbi Levi said: to what is the matter comparable? To a priest who had a slave. The priest went out from the province, and his slave went to seek him among the graves. He began to cry out, "My master! My master!" They said to him, "Who is your master?" He said to them, "So-and-so the priest." They said to him, "Fool of the world, do you seek a priest in a cemetery?" So Pharaoh said to Moses, "Who is the LORD? I have brought out the register of deities and sought Him within it and did not find Him." He said to him, "Fool of the world, the deities in your hand are dead, but our God is living and enduring," as it is said (Jeremiah 10:10), "But the LORD God is truth; He is the living God and the everlasting King."
Pharaoh Searches His Register of Gods for the LORD
Yalkut Shimoni on Torah 175:1
אָמַר רַבִּי חִיָּיא בַּר אַבָּא, יוֹם גִינוּסְיָא הָיָה, וְהָיוּ כָּל הַמְּלָכִים בָּאִים וּמְעַטְּרִים אוֹתוֹ, שֶׁהָיָה קוֹזְמָטוֹר, וְהָיוּ מֹשֶׁה וְאַהֲרֹן עוֹמְדִין עַל פֶּתַח פְּלָטִין, נִכְנְסוּ אֵצֶל פַּרְעֹה וְאָמְרוּ לוֹ שְׁנֵי זְקֵנִים עוֹמְדִין עַל פֶּתַח פְּלָטִין שֶׁלְּךָ, אָמַר לָהֶם וְיֵשׁ בְּיָדָם עֲטָרוֹת, אָמְרוּ לוֹ לָאו, אָמַר לָהֶם בָּאַחֲרוֹנָה יִכָּנְסוּ. נִכְנְסוּ אֵצֶל פַּרְעֹה, אָמַר לָהֶם, מָה אַתֶּם מְבַקְּשִׁים, אָמְרוּ לוֹ, (שמות ז, טז) "אֱלֹהֵי הָעִבְרִים שְׁלָחַנִי אֵלֶיךָ" שַׁלַּח אֶת עַמִּי וְיָחֹגּוּ לִי בַּמִּדְבָּר, אָמַר לָהֶם, מִי ה' אֲשֶׁר אֶשְׁמַע בְּקֹלוֹ, וְלֹא הָיָה יוֹדֵעַ לִשְׁלֹחַ לִי עֲטָרָה מִשֶּׁלּוֹ, אֶלָּא בִּדְבָרִים בָּא אֵלַי, מִי ה' אֲשֶׁר אֶשְׁמַע בְּקֹלוֹ. אָמַר רַבִּי לֵוִי, הוֹצִיא בְּאוֹתָהּ שָׁעָה דִיפְתְּרָא שֶׁל אֱלָהוּת, וְקָרָא, אֱלֹהֵי אֱדוֹם מוֹאָב וְצִידוֹן, אָמַר לָהֶם, הֲרֵי קָרָאתִי וְאֵינִי מוֹצֵא מַה שֶּׁאַתֶּם אוֹמְרִים. אָמַר רַבִּי לֵוִי, לְמָה הַדָּבָר דּוֹמֶה, לְכֹהֵן שֶׁהָיָה לוֹ עֶבֶד, יָצָא הַכֹּהֵן מִן הַמְּדִינָה, הָלַךְ עַבְדּוֹ לְבַקְּשׁוֹ בֵּין הַקְּבָרוֹת, הִתְחִיל צוֹוֵחַ אֲדוֹנִי אֲדוֹנִי, אָמְרוּ לוֹ מִי הוּא אֲדוֹנְךָ, אָמַר לָהֶם פְּלוֹנִי כֹּהֵן, אוֹמְרִים לוֹ, שׁוֹטֶה שֶׁבָּעוֹלָם, כֹּהֵן אַתָּה מְבַקֵּשׁ בְּבֵית הַקְּבָרוֹת, כָּךְ אָמַר פַּרְעֹה לְמֹשֶׁה מִי ה', הוֹצֵאתִי דִיפְתְּרָא שֶׁל אֱלָהוּת וּבִקַּשְׁתִּיו בְּתוֹכָהּ וְלֹא מְצָאתִיו, אָמַר לֵיהּ, שׁוֹטֶה שֶׁבָּעוֹלָם, הָאֱלוֹהוּת שֶׁבְּיָדְךָ מֵתִים הֵם אֲבָל אֱלֹהֵינוּ חַי וְקַיָּם הוּא, שֶׁנֶּאֱמַר (ירמיהו י, י) "וַה' אֱלֹהִים אֱמֶת הוּא אֱלֹהִים חַיִּים [וּ]מֶלֶךְ עוֹלָם".