Maimonides, "Mishneh Torah", Sefer ha-Madda
Maimonides, Mishneh Torah, Sefer ha-Madda, Torah Study, Chapter 4, Halachah 5
A disciple should not feel ashamed before his fellow-students who grasp the lesson after hearing it once or twice, while he needs to hear it several times before he knows it. For if this makes him feel ashamed, he will go through college without having learnt anything.
The ancient sages accordingly said, “A bashful man cannot learn, nor a passionate man teach” (Ethics of the Fathers 2:6).
These observations only apply when the students’ lack of understanding is due to the difficulty of the subject or to their mental deficiency. But if the teacher clearly sees that they are negligent and indolent in their study of the Torah and that this is the cause of their failure to understand, it is his duty to scold them and shame them with words of reproach, and so stimulate them to be keen. And in this regard, the sages said “Arouse awe in the pupils”.
It is thus improper for a teacher to indulge in frivolity before his pupils, or to jest in their presence, or eat and drink with them—so that the fear of him be upon them, and they will thus learn from him quickly.1 2
לֹא יִהְיֶה הַתַּלְמִיד בּוֹשׁ מֵחֲבֵרָיו שֶׁלָּמְדוּ מִפַּעַם רִאשׁוֹנָה אוֹ שְׁנִיָּה וְהוּא לֹא לָמַד אֶלָּא אַחַר כַּמָּה פְּעָמִים. שֶׁאִם נִתְבַּיֵּשׁ מִדָּבָר זֶה נִמְצָא נִכְנָס וְיוֹצֵא לְבֵית הַמִּדְרָשׁ וְהוּא אֵינוֹ לָמֵד כְּלוּם. לְפִיכָךְ אָמְרוּ חֲכָמִים הָרִאשׁוֹנִים אֵין הַבַּיְשָׁן לָמֵד וְלֹא הַקַּפְּדָן מְלַמֵּד. בַּמֶּה דְּבָרִים אֲמוּרִים בִּזְמַן שֶׁלֹּא הֵבִינוּ הַתַּלְמִידִים הַדָּבָר מִפְּנֵי עָמְקוֹ אוֹ מִפְּנֵי דַּעְתָּן שֶׁהִיא קְצָרָה. אֲבָל אִם נִכָּר לָרַב שֶׁהֵם מִתְרַשְּׁלִין בְּדִבְרֵי תּוֹרָה וּמִתְרַפִּין עֲלֵיהֶן וּלְפִיכָךְ לֹא הֵבִינוּ חַיָּב לִרְגֹז עֲלֵיהֶן וּלְהַכְלִימָן בִּדְבָרִים כְּדֵי לְחַדְּדָם. וּכְעִנְיָן זֶה אָמְרוּ חֲכָמִים זְרֹק מָרָה בַּתַּלְמִידִים. לְפִיכָךְ אֵין רָאוּי לָרַב לִנְהֹג קַלּוּת רֹאשׁ לִפְנֵי הַתַּלְמִידִים וְלֹא לִשְׂחֹק בִּפְנֵיהֶם וְלֹא לֶאֱכל וְלִשְׁתּוֹת עִמָּהֶם כְּדֵי שֶׁתְּהֵא אֵימָתוֹ עֲלֵיהֶן וְיִלְמְדוּ מִמֶּנּוּ בִּמְהֵרָה: