(Exodus 17:2) "And the people quarreled with Moses." They overstepped the line of justice. It is the way of the world that a person grows angry within his household and sets his eyes only on the youngest; but these set their eyes only on the greatest. Therefore it is said, "And the people quarreled with Moses," and not with Aaron, for Aaron was beloved to them, since he loved peace and pursued peace. This is what Scripture says (Proverbs 18:6), "The lips of a fool enter into strife." They were demanding, "Would that we had died by the hand of the LORD" (Numbers 20:3), "and would that we had perished." What is the meaning of "before the LORD"? A parable of a prince who had no manners, who would climb the walls and the trees against his father, and go to the place of the wild beasts so that his father would be pained. So these were saying, "Let us die so that He will be pained over us." And not only that, but He swore to our fathers to give us the land.
Why the People Quarreled With Moses and Not Aaron
Yalkut Shimoni on Torah 261:14
(שמות יז ב) וַיָּרֶב הָעָם עִם מֹשֶׁה. עָבְרוּ עַל שׁוּרַת הַדִּין, דֶּרֶךְ אֶרֶץ אָדָם כּוֹעֵס בְּתוֹךְ בֵּיתוֹ וְאֵינוֹ נוֹתֵן עֵינָיו אֶלָּא בְּקָטָן, אֲבָל אֵלּוּ לֹא נָתְנוּ עֵינָם אֶלָּא בַּגָדוֹל, לְכָךְ נֶאֱמַר וַיָּרֶב הָעָם עִם מֹשֶׁה, וְלֹא עִם אַהֲרֹן, שֶׁהָיָה אַהֲרֹן חָבִיב עֲלֵיהֶם, שֶׁהָיָה אוֹהֵב שָׁלוֹם וְרוֹדֵף שָׁלוֹם. זֶה שֶׁאָמַר הַכָּתוּב (משלי יח, ו) "שִׂפְתֵי כְסִיל יָבֹאוּ בְּרִיב", הָיוּ תוֹבְעִין "מִי יִתֵּן מוֹתֵנוּ בְּיַד ה'", (במדבר כ, ג) "וְלוּ גָּוַעְנוּ". מַהוּ "לִפְנֵי ה'", מָשָׁל לְבֶן מְלָכִים שֶׁלֹּא הָיָה לוֹ תַּרְבּוּת, וְהָיָה עוֹלֶה לַכְּתָלִים וְלָאִילָנוֹת כְּנֶגֶד אָבִיו, הוֹלֵךְ לִמְקוֹם הַחַיּוֹת כְּדֵי שֶׁיְּהֵא אָבִיו מִצְטָעֵר, כַּךְ הָיוּ אֵלּוּ אוֹמְרִים, אָנוּ מֵתִים שֶׁיְּהֵא מִצְטָעֵר עָלֵינוּ, וְלֹא עוֹד אֶלָּא שֶׁנִּשְׁבַּע לַאֲבוֹתֵינוּ לָתֵת לָנוּ אֶת הָאָרֶץ.