Midrash for Chagigah 5:3

והתם מנלן דכתיב (דברים לא, יב) למען ישמעו ולמען ילמדו ותניא למען ישמעו פרט למדבר ואינו שומע ולמען ילמדו פרט לשומע ואינו מדבר

And there, how do we know [that those who are mute or deaf are exempt from the assembly]? Because it is written,(Deuteronomy 31:12) "that they may hear and that they may learn." And it was taught in a Baraita: "That they may hear" - excluding he who speaks and does not hear; "and that they may learn" - excluding he who hears and does not speak. Is this to say, that he who cannot talk cannot learn?

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