recovered from “Talmud Kiddushin 30a”
Kiddushin
קידושין ל׳ א — ד"ה וַאֲבִי אָבִיו מִי מִיחַיַּיב
Kiddushin 30a:5
The passage discusses the obligation to teach Torah to one's children and descendants, explaining that one who teaches their son Torah is credited as if they taught not only that son but all future generations, equivalent to receiving the Torah at Mount Sinai.
וַאֲבִי אָבִיו מִי מִיחַיַּיב? וְהָתַנְיָא: ״וְלִמַּדְתֶּם אֹתָם אֶת בְּנֵיכֶם״ – וְלֹא בְּנֵי בְנֵיכֶם. וּמָה אֲנִי מְקַיֵּים: ״וְהוֹדַעְתָּם לְבָנֶיךָ וְלִבְנֵי בָנֶיךָ״, לוֹמַר לָךְ: שֶׁכׇּל הַמְלַמֵּד אֶת בְּנוֹ תּוֹרָה – מַעֲלֶה עָלָיו הַכָּתוּב כְּאִילּוּ לִמְּדוֹ לוֹ וְלִבְנוֹ וּלְבֶן בְּנוֹ, עַד סוֹף כׇּל הַדּוֹרוֹת! אָמַר רַבִּי יְהוֹשֻׁעַ בֶּן לֵוִי: כׇּל הַמְלַמֵּד אֶת בֶּן בְּנוֹ תּוֹרָה מַעֲלֶה עָלָיו הַכָּתוּב כְּאִילּוּ קִבְּלָהּ מֵהַר סִינַי, שֶׁנֶּאֱמַר: ״וְהוֹדַעְתָּם לְבָנֶיךָ וְלִבְנֵי בָנֶיךָ״, וּסְמִיךְ לֵיהּ: ״יוֹם אֲשֶׁר עָמַדְתָּ לִפְנֵי ה׳ אֱלֹקֶיךָ בְּחֹרֵב״.
The Gemara asks: But is one’s father’s father obligated to teach him Torah? But isn’t it taught in a baraita, that the verse: “And you shall teach them to your sons” (Deuteronomy 11:19), indicates: But not your sons’ sons? And how do I realize, i.e., understand, the meaning of the verse: “But make them known to your sons and to your sons’ sons” (Deuteronomy 4:9)? This serves to say to you that whoever teaches his son Torah, the verse ascribes him credit as though he taught him, and his son, and his son’s son, until the end of all generations. Rabbi Yehoshua ben Levi says: Anyone who teaches his son’s son Torah, the verse ascribes him credit as though he received it from Mount Sinai, as it is stated: “But make them known to your sons and to your sons’ sons,” and juxtaposed to it is the phrase in the verse: “The day when you stood before the Lord your God in Horeb” (Deuteronomy 4:10), as Horeb is Mount Sinai.