וְהַכֹּהֵן֩ הַגָּד֨וֹל מֵאֶחָ֜יו אֲֽשֶׁר־יוּצַ֥ק עַל־רֹאשׁ֣וֹ ׀ שֶׁ֤מֶן הַמִּשְׁחָה֙ וּמִלֵּ֣א אֶת־יָד֔וֹ לִלְבֹּ֖שׁ אֶת־הַבְּגָדִ֑ים אֶת־רֹאשׁוֹ֙ לֹ֣א יִפְרָ֔ע וּבְגָדָ֖יו לֹ֥א יִפְרֹֽם׃
And the priest that is highest among his brethren, upon whose head the anointing oil is poured, and that is consecrated to put on the garments, shall not let the hair of his head go loose, nor rend his clothes;
Pirkei Avot
Rabbi Ishmael his son said: He who learns in order to teach, it is granted to him to study and to teach; But he who learns in order to practice, it is granted to him to learn and to teach and to practice. Rabbi Zadok said: do not make them a crown for self-exaltation, nor a spade with which to dig. So too Hillel used to say, “And he that puts the crown to his own use shall perish.” Thus you have learned, anyone who derives worldly benefit from the words of the Torah, removes his life from the world.