מִי שֶׁאֵינוֹ לֹא בְּמִקְרָא וְלֹא בְּמִשְׁנָה וְלֹא בְּדֶרֶךְ אֶרֶץ הֲרֵי זֶה בְּחֶזְקַת רָשָׁע וּפָסוּל לְעֵדוּת מִדִּבְרֵיהֶם. שֶׁכָּל מִי שֶׁיָּרַד עַד כָּךְ חֲזָקָה שֶׁהוּא עוֹבֵר עַל רֹב הָעֲבֵרוֹת שֶׁיָּבוֹאוּ לְיָדוֹ:
When one does not read the Written Law, nor study the Oral Law, nor carry on ordinary social relationships, he can be assumed to be wicked and is disqualified as a witness according to Rabbinic decree. The rationale is that whenever a person has descended to such a degree, it can be assumed that he will transgress most transgressions that will present themselves to him.
