This is what Scripture says: "Hatred stirs up strife" (Proverbs 10:12). The "hatred" that Aaron placed between Israel and their Father in heaven "stirs up strife" — it stirred up against them severe judgments. Rabbi Assi said: this teaches that Aaron used to take their offering and slacken it for them, saying to them, "Know that these have no substance." This is what the Holy One, blessed be He, said to Moses, "Whoever has sinned against Me, him will I blot out of My book" (Exodus 32:33). This is what is written, "And the LORD was very angry with Aaron, to destroy him" (Deuteronomy 9:20). Rabbi Joshua of Sikhnin said in the name of Rabbi Levi: the destruction written here means nothing but the loss of his children, as you say, "And I destroyed his fruit above" (Amos 2:9). "And love covers over all transgressions" (Proverbs 10:12) — the prayer that Moses prayed for him. What did he pray for him? Rabbi Mani of Sikhnin said in the name of Rabbi Levi: from the beginning of the book until here it is written, "And the sons of Aaron shall offer," "And the sons of Aaron shall put," "And the sons of Aaron shall arrange," "And the sons of Aaron shall burn" (Leviticus 1-3). Moses said before the Holy One, blessed be He: "A hated well, yet its waters are beloved. To the wood You apportioned honor for the sake of their offspring, as we have learned: all kinds of wood are fit for the arrangement on the altar except that of the olive and the vine. To Aaron will You not apportion honor for the sake of his sons?" The Holy One, blessed be He, said to him: "By your life, at your prayer I draw him near; and not only that, but I make him the essence and his sons secondary," as it is said, "Command Aaron and his sons."
Moses Prays and Aaron Becomes the Essence
Yalkut Shimoni on Torah 479:17
זֶה שֶׁאָמַר הַכָּתוּב "שִׂנְאָה תְעוֹרֵר מְדָנִים" "שִׂנְאָה" שֶׁנָּתַן אַהֲרֹן בֵּין יִשְׂרָאֵל לַאֲבִיהֶם שֶׁבַּשָּׁמַיִם "תְּעוֹרֵר מְדָנִים", עוֹרְרָה עֲלֵיהֶם דִּינֵי דִינִים. אָמַר רַבִּי אַסֵּי מְלַמֵּד שֶׁהָיָה (הַקָּדוֹשׁ בָּרוּךְ הוּא) [אַהֲרֹן] נוֹטֵל אֶת (קַרְנָם וּפוֹתְחוֹ) [קָרְבָּנָם וּפוֹחֲסוֹ] לָהֶם וְאוֹמֵר לָהֶם דְּעוּ שֶׁאֵין לָהֶן מַמָּשׁ. הוּא שֶׁהַקָּדוֹשׁ בָּרוּךְ הוּא אוֹמֵר לְמֹשֶׁה (שמות לב, לג) "מִי אֲשֶׁר חָטָא לִי אֶמְחֶנּוּ מִסִּפְרִי". הֲדָא הוּא דִכְתִיב "וּבְאַהֲרֹן הִתְאַנַּף ה' מְאֹד לְהַשְׁמִידוֹ". רַבִּי יְהוֹשֻׁעַ דְּסִיכְנִין בְּשֵׁם רַבִּי לֵוִי אֵין הַשְׁמָדָה הַכְּתוּבָה כָּאן אֶלָּא כִּלּוּי בָּנִים. כְּמָה דְּאַתְּ אָמַר (עמוס ב, ט) "וָאַשְׁמִיד פִּרְיוֹ מִמַּעַל" וְגוֹ'. (משלי שם) "וְעַל כָּל פְּשָׁעִים תְּכַסֶּה אַהֲבָה". תְּפִלָּה שֶׁנִּתְפַּלֵּל מֹשֶׁה עָלָיו. מַה נִּתְפַּלֵּל עָלָיו, רַבִּי מָנִי דְּסִיכְנִין בְּשֵׁם רַבִּי לֵוִי אָמַר, מִתְּחִלַּת הַסֵּפֶר וְעַד כָּאן כָּתוּב "וְהִקְרִיבוּ בְּנֵי אַהֲרֹן" (שם ז) "וְנָתְנוּ בְּנֵי אַהֲרֹן" (שם ח) "וְעָרְכוּ בְּנֵי אַהֲרֹן" (ויקרא ג, ה) "וְהִקְטִירוּ בְּנֵי אַהֲרֹן". אָמַר מֹשֶׁה לִפְנֵי הַקָּדוֹשׁ בָּרוּךְ הוּא, בְּאֵר שְׂנוּאָה וּמֵימֶיהָ חֲבִיבִין, לָעֵצִים חָלַקְתָּ כָּבוֹד בִּשְׁבִיל בְּנֵיהֶן כְּדִתְנַן כָּל הָעֵצִים כְּשֵׁרִין לְמַעֲרָכָה חוּץ מִשֶּׁל זַיִת וְשֶׁל גֶּפֶן, לְאַהֲרֹן אִי אַתָּה חוֹלֵק כָּבוֹד בִּשְׁבִיל בָּנָיו. אָמַר לוֹ הַקָּדוֹשׁ בָּרוּךְ הוּא חַיֶּיךָ שֶׁבִּתְפִלָּתְךָ אֲנִי מְקַרְבוֹ, וְלֹא עוֹד אֶלָּא שֶׁאֲנִי עוֹשֶׂה אוֹתוֹ עִקָּר וּבָנָיו טְפֵלִים שֶׁנֶּאֱמַר "צַו אֶת אַהֲרֹן וְאֶת בָּנָיו".