Mishneh Torah — Transmission of the Oral Law מסירת תורה שבעל פה, Chapter 22

כָּל אֵלּוּ הַחֲכָמִים הַנִּזְכָּרִים, הֶם גְּדוֹלֵי הַדּוֹרוֹת – מֵהֶם רָאשֵׁי יְשִׁיבוֹת, וּמֵהֶם רָאשֵׁי גָּלִיּוֹת, וּמֵהֶם מִסַּנְהֶדְּרֵי גְּדוֹלָה. וְעִמָּהֶם בְּכָל דּוֹר וָדוֹר, אֲלָפִים וּרְבָבוֹת שֶׁשָּׁמְעוּ מֵהֶם וְעִמָּהֶם.

Thus, [the source of] all these people's knowledge is God, the Lord of Israel. All the sages who were mentioned were the leaders of the generations. Among them were heads of academies, heads of the exile, and members of the great Sanhedrin. Together with them in each generation, there were thousands and myriads that heard their [teachings].