Another interpretation: I place My wrath and My fear upon Egypt. "Wrath" means nothing but fury, as it is said, "He sent upon them the fierceness of His anger, wrath and indignation and trouble" (Psalms 78:49). And it says, "That day is a day of wrath" (Zephaniah 1:15). "And I will smite every firstborn." I might understand this to be by means of an angel or by means of a messenger; therefore the verse states, "And the LORD smote every firstborn in the land of Egypt" (Exodus 12:29) - not by means of an angel and not by means of a messenger. "And I will smite every firstborn in the land of Egypt" - even those from other places. From where do we learn the firstborn of Egypt who were in other places? As it is said, "To Him who smote Egypt through their firstborn" (Psalms 136:10). From where the firstborn of Ham, Cush, Put, and Lud? The verse states, "And He smote all the firstborn in Egypt, the first of their strength in the tents of Ham" (Psalms 78:51). "From man to beast" - from the one who began the transgression the punishment began, as in the case of "And the men who were at the entrance of the house" (Genesis 19:11). And these are matters argued from the lesser to the greater: if with the measure of punishment, which is the smaller, the punishment began with the one who began the transgression, how much more so with the measure of goodness, which is the greater. "And against all the gods of Egypt I will execute judgments" - each different from the other: those of stone would melt, those of wood would rot, those of metal would rust, as it is said, "While Egypt was burying those whom the LORD had smitten among them, every firstborn; and against their gods the LORD executed judgments" (Numbers 33:4). And some say: those of stone would rot and those of wood would melt. Rabbi Nathan says: judgments and judgments of judgments - they rotted, split, were hewn down, were burned. We thus learn that the idols were struck in four ways and their worshipers in three: by plague, by destruction, by pestilence. "I am the LORD" - that which flesh and blood cannot say. "I am the LORD": by an oath I exact payment from them. And these are matters argued from the lesser to the greater: if with the smaller measure of punishment the Holy One, blessed be He, said He would act and did so, with the greater measure of goodness how much more so. "And I will pass through the land of Egypt" - I and not an angel; "and I will smite every firstborn" - I and not a seraph, and so forth. There is no nation that is struck whose god is not struck along with it, as it is said, "And against all the gods of Egypt I will execute judgments."
The LORD Alone Struck Egypt's Firstborn and Judged Its Gods
Yalkut Shimoni on Torah 199:5
דָּבָר אַחֵר, נוֹתֵן אֲנִי עֶבְרָתִי וְיִרְאָתִי בְּמִצְרַיִם, וְאֵין עֶבְרָה אֶלָּא זַעַם, שֶׁנֶּאֱמַר "יְשַׁלַּח בָּם חֲרוֹן אַפּוֹ עֶבְרָה וָזַעַם וְצָרָה". וְאוֹמֵר (צפניה א, טו) "יוֹם עֶבְרָה הַיּוֹם הַהוּא". וְהִכֵּיתִי כָל בְּכוֹר. שׁוֹמֵעַ אֲנִי עַל יְדֵי מַלְאָךְ אוֹ עַל יְדֵי שָׁלִיחַ, תַּלְמוּד לוֹמַר (להלן פסוק כט) "וַה' הִכָּה כָל בְּכוֹר בְּאֶרֶץ מִצְרַיִם", לֹא עַל יְדֵי מַלְאָךְ וְלֹא עַל יְדֵי שָׁלִיחַ. וְהִכֵּיתִי כָל בְּכוֹר בְּאֶרֶץ מִצְרַיִם, וַאֲפִלּו מִמְּקוֹמוֹת אֲחֵרִים, בְּכוֹרֵי מִצְרַיִם שֶׁהֵן בִּמְקוֹמוֹת אֲחֵרִים מִנַּיִן, שֶׁנֶּאֱמַר "לְמַכֵּה מִצְרַיִם בִּבְכוֹרֵיהֶם". בְּכוֹרֵי חָם, כּוּשׁ, פּוּט וְלוּד מִנַּיִן, תַּלְמוּד לוֹמַר (שם עח, נא) "וַיַּךְ כָּל בְּכוֹר בְּמִצְרָיִם רֵאשִׁית אוֹנִים בְּאָהֳלֵי חָם". מֵאָדָם וְעַד בְּהֵמָה, מִי שֶׁהִתְחִיל בַּעֲבֵרָה מִמֶּנּוּ הִתְחִילָה הַפֻּרְעָנוּת, כַּיּוֹצֵא בּוֹ (בראשית יט, יא) "וְאֶת הָאֲנָשִׁים אֲשֶׁר פֶּתַח הַבַּיִת" (כָּתוּב בְּרֶמֶז פ"ד) וַהֲרֵי דְּבָרִים קַל וָחֹמֶר, וּמָה אִם מִדַּת הַפֻּרְעָנוּת מְעוּטָה מִמֶּנּוּ הִתְחִילָה הַפֻּרְעָנוּת מִמִּי שֶׁהִתְחִיל בַּעֲבֵרָה, קַל וָחֹמֶר לְמִדַּת הַטּוֹב שֶׁהִיא מְרֻבָּה. וּבְכָל אֱלֹהֵי מִצְרַיִם אֶעֱשֶׂה שְׁפָטִים, מְשֻׁנִּים זֶה מִזֶּה, שֶׁל אֶבֶן הָיְתָה נְמֶסֶת, שֶׁל עֵץ הָיְתָה נִרְקֶבֶת, שֶׁל מַתֶּכֶת נַעֲשֶׂה חֲלוּדָה, שֶׁנֶּאֱמַר "וּמִצְרַיִם מְקַבְּרִים אֶת אֲשֶׁר הִכָּה ה' בָּהֶם כָּל בְּכוֹר וּבֵאלֹהֵיהֶם עָשָׂה ה' שְׁפָטִים. וְיֵשׁ אוֹמְרִים, שֶׁל אֶבֶן נִרְקֶבֶת וְשֶׁל עֵץ נְמֶסֶת, רַבִּי נָתָן אוֹמֵר שְׁפָטִים וּשְׁפָטֵי שְׁפָטִים נִרְקָבִים נִבְקָעִים נִגְדָּעִים נִשְׂרָפִים. נִמְצִינוּ לְמֵדִים שֶׁהָאֱלִילִים לוֹקִים בְּאַרְבַּע דְּבָרִים וְעוֹבְדֵיהֶם בִּשְׁלֹשָׁה, בְּמַכָּה, בְּהַשְׁחָתָה בְּמַגֵּפָה אֲנִי ה'. מַה שֶּׁאִי אֶפְשָׁר לְבָשָׂר וָדָם לוֹמַר כֵּן, אֲנִי ה', בִּשְׁבוּעָה אֲנִי נִפְרָע מֵהֶם, וַהֲלֹא דְּבָרִים קַל וָחֹמֶר, וּמָה אִם מִדַּת פֻּרְעָנוּת מְעוּטָה אָמַר הַקָּדוֹשׁ בָּרוּךְ הוּא לַעֲשׂוֹת וְעָשָׂה, לְמִדַּת טוֹבָה שֶׁמְּרֻבָּה עַל אַחַת כַּמָּה וְכַמָּה. וְעָבַרְתִּי בְאֶרֶץ מִצְרַיִם, אֲנִי וְלֹא מַלְאָךְ, וְהִכֵּיתִי כָּל בְּכוֹר, אֲנִי וְלֹא שָׂרָף וְכוּ'. אֵין לְךָ כָּל אֻמָּה וְאֻמָּה שֶׁלּוֹקָה שֶׁאֵין אֱלֹהֶיהָ לוֹקֶה עִמָּהּ, שֶׁנֶּאֱמַר וּבְכָל אֱלֹהֵי מִצְרַיִם אֶעֱשֶׂה שְׁפָטִים.