Matot, Siman 7 מטות, ז׳
1 א

וּמִקְנֶה רַב. זֶה שֶׁאָמַר הַכָּתוּב: לֵב חָכָם לִימִינוֹ וְגוֹ' (קהלת י, ב). לֵב חָכָם לִימִינוֹ, זֶה מֹשֶׁה. וְלֵב כְּסִיל לִשְׂמֹאלוֹ, אֵלּוּ בְּנֵי רְאוּבֵן וּבְנֵי גָד, שֶׁעָשׂוּ אֶת הָעִקָּר טָפֵל, וְהַטָּפֵל עִקָּר. לָמָּה, שֶׁחִבְּבוּ נִכְסֵיהֶם יוֹתֵר מִגּוּפָן, שֶׁאָמְרוּ לְמֹשֶׁה, גִּדְרוֹת צֹאן נִבְנֶה לְמִקְנֵינוּ פֹּה, פֹּה תְּחִלָּה, וְאַחַר כָּךְ, וְעָרִים לְטַפֵּנוּ. אָמַר לָהֶם מֹשֶׁה, לֹא תַּעֲשׂוּ כָּךְ. עֲשׂוּ אֶת הָעִקָּר תְּחִלָּה. בְּנוּ עָרִים לְטַפְּכֶם. וְאַחַר כָּךְ גְּדֵרוֹת לְצֹאנְכֶם. הֱוֵי, לֵב חָכָם לִימִינוֹ, זֶה מֹשֶׁה. וְלֵב כְּסִיל לִשְׂמֹאלוֹ, אֵלּוּ בְּנֵי רְאוּבֵן וּבְנֵי גָּד. אָמַר לָהֶם הַקָּדוֹשׁ בָּרוּךְ הוּא, אַתֶּם חִבַּבְתֶּם מָמוֹנְכֶם יוֹתֵר מִנַּפְשׁוֹתֵיכֶם. חַיֵּיכֶם, אֵין בּוֹ בְּרָכָה, שֶׁנֶּאֱמַר: נַחֲלָה מְבֹהֶלֶת בָּרִאשׁוֹנָה וְאַחֲרִיתָהּ לֹא תְּבֹרַךְ (משלי כ, כא). אֶל תִּיגַע לְהַעֲשִׁיר, מִבִּינָתְךָ חֲדָל (משלי כג, ד). וְאֵיזוֹ עָשִׁיר. הַשָּׂמֵחַ בְּחֶלְקוֹ, שֶׁנֶּאֱמַר: יְגִיעַ כַּפֶּיךָ כִּי תֹּאכֵל, אַשְׁרֶיךָ וְטוֹב לָךְ (תהלים קכח, ב).

"And much cattle" (Numbers 32:1). This is [the meaning of] that which is stated by the verse (Ecclesiastes 10:2), "A wise man’s heart is to his right," that is Moshe; "but a fool’s heart is to his left," that is the Children of Reuven and the Children of Gad, who made the essential, secondary, and the secondary, essential. Why? Because they loved their possessions more than their selves. As they said to Moshe (Numbers 32:16), "'We will build here sheepfolds for our flocks,' first, and afterwards, 'and towns for our children.'" Moshe said to them, "Do not do like this, make the essential first; 'build towns for your children,' and afterwards 'sheepfolds for your flocks' (Numbers 32:24)." Hence, "A wise man’s heart is to his right," that is Moshe; "but a fool’s heart is to his left," that is the Children of Reuven and the Children of Gad. The Holy One, blessed be He, said to them, "You loved your money more than your souls. By your lives, there is no blessing in this, as stated (Proverbs 20:21), 'An estate acquired in haste at the outset will not be blessed in the end.'" "Do not toil to gain wealth; have the sense to desist" (Proverbs 23:4). And who is wealthy? One who is happy with his lot, as stated (in Psalms 128:2), "You shall eat the produce of your hands; you shall be happy, and it shall go well with you."