Reference for Pirkei Avot 6:4
כַּךְ הִיא דַּרְכָּהּ שֶׁל תּוֹרָה, פַּת בְּמֶלַח תֹּאכַל, וּמַיִם בִּמְשׂוּרָה תִשְׁתֶּה, וְעַל הָאָרֶץ תִּישַׁן, וְחַיֵּי צַעַר תִּחְיֶה, וּבַתּוֹרָה אַתָּה עָמֵל, אִם אַתָּה עֹשֶׂה כֵן, (תהלים קכח) אַשְׁרֶיךָ וְטוֹב לָךְ. אַשְׁרֶיךָ בָּעוֹלָם הַזֶּה וְטוֹב לָךְ לָעוֹלָם הַבָּא:
This is the way of Torah: A loaf with salt shall you eat, and water by measure shall you drink, and on the ground shall you sleep, and a life of travail shall you live, and in Torah shall you toil. And if you do so — you are fortunate and it is good for you. You are fortunate in this world and it is good for you in the world to come. Do not seek greatness for yourself, and do not lust for honor. More than your learning, do! And do not lust for the table of princes. For your table is greater than theirs, and your crown is greater than theirs, and your Master is trusted to pay you the wage of your work.