אֵין מְלַמְּדִין תּוֹרָה אֶלָּא לְתַלְמִיד הָגוּן נָאֶה בְּמַעֲשָׂיו. אוֹ לְתָם. אֲבָל אִם הָיָה הוֹלֵךְ בְּדֶרֶךְ לֹא טוֹבָה מַחְזִירִין אוֹתוֹ לַמּוּטָב וּמַנְהִיגִין אוֹתוֹ בְּדֶרֶךְ יְשָׁרָה וּבוֹדְקִין אוֹתוֹ וְאַחַר כָּךְ מַכְנִיסִין אוֹתוֹ לְבֵית הַמִּדְרָשׁ וּמְלַמְּדִין אוֹתוֹ. אָמְרוּ חֲכָמִים כָּל הַשּׁוֹנֶה לְתַלְמִיד שֶׁאֵינוֹ הָגוּן כְּאִלּוּ זָרַק אֶבֶן לְמַרְקוּלִיס שֶׁנֶּאֱמַר (משלי כו ח) "כִּצְרוֹר אֶבֶן בְּמַרְגֵּמָה כֵּן נוֹתֵן לִכְסִיל כָּבוֹד". וְאֵין כָּבוֹד אֶלָּא תּוֹרָה שֶׁנֶּאֱמַר (משלי ג לה) "כָּבוֹד חֲכָמִים יִנְחָלוּ". וְכֵן הָרַב שֶׁאֵינוֹ הוֹלֵךְ בְּדֶרֶךְ טוֹבָה אַף עַל פִּי שֶׁחָכָם גָּדוֹל הוּא וְכָל הָעָם צְרִיכִין לוֹ אֵין מִתְלַמְּדִין מִמֶּנּוּ עַד שׁוּבוֹ לַמּוּטָב. שֶׁנֶּאֱמַר (מלאכי ב ז) "כִּי שִׂפְתֵי כֹהֵן יִשְׁמְרוּ דַעַת וְתוֹרָה יְבַקְשׁוּ מִפִּיהוּ כִּי מַלְאַךְ ה' צְבָאוֹת הוּא". אָמְרוּ חֲכָמִים אִם הָרַב דּוֹמֶה לְמַלְאַךְ ה' צְבָאוֹת תּוֹרָה יְבַקְּשׁוּ מִפִּיהוּ אִם לָאו אַל יְבַקְּשׁוּ תּוֹרָה מִפִּיהוּ:
Torah should be taught only to a proper student - one whose deeds are attractive - or to a person whose behavior is unknown. However, [a potential student] who follows bad ways should be influenced to correct his behavior and trained to follow a straight path. [After he repents, his deeds] are examined and he is allowed to enter the house of study to be instructed. Our Sages said: Whoever teaches an improper student is considered as if he throws a stone to Mercury, as [Proverbs 26:8] states: "As one who winds a stone in a sling, so is he who gives honor to a fool." There is no "honor" other than Torah, as [Proverbs 3:35] states: "The wise shall inherit honor." Similarly, one should not study from a teacher who does not follow a proper path, even though he is a very wise man and his [instruction] is required by the entire nation, until he returns to a good path, as [implied by Malachi 2:7]: "For the priest's lips shall keep knowledge, and they shall seek Torah from his mouth, because he is a messenger from the Lord of Hosts." Our Sages said: If a teacher resembles "a messenger of the Lord of Hosts," seek Torah from his mouth. If he does not, do not seek Torah from his mouth.
