רָ֘חַ֤שׁ לִבִּ֨י ׀ דָּ֘בָ֤ר ט֗וֹב אֹמֵ֣ר אָ֭נִי מַעֲשַׂ֣י לְמֶ֑לֶךְ לְ֝שׁוֹנִ֗י עֵ֤ט ׀ סוֹפֵ֬ר מָהִֽיר׃
עס ייִרט מײַן האַרץ מיטן שײנעם װאָרט, איך װעל פֿירזאָגן מײַנע לידער צום מלך;מײַן צונג איז די פּען פֿון אַ שרײַבער אַ פֿלינקן.
Mishneh Torah, Torah Study
A teacher of school children who leaves the children and departs from the school, or who engages himself in another kind of work while he is with them, or who is negligent in teaching them, behold, he is included among those of whom it is said: "Cursed be he that doeth the work of the Lord with a slack hand" (Jer. 48.10). It is, therefore, improper to appoint any teacher save one who is God fearing, diligent in reading and grammar.3Baba Batra, 21b. C.