Yehudai ben Nahman (or Yehudai Gaon; Hebrew: יהודאי גאון, sometimes: Yehudai b. Nahman) was the head of the yeshiva in Sura from 757 to 761, during the Gaonic period of Judaism. He was originally a member of the academy of Pumbedita, but the exilarch Solomon ben Hisdai appointed him as Gaon of Sura as "there is no one there (at Sura) as distinguished as he is for wisdom".
He waged a strong campaign, continued by his disciple Pirkoi ben Bavoi, for the acceptance of the Babylonian Talmud as the standard for Jewish law in all countries. This was opposed by the Jews of Eretz Yisrael, who relied on the Jerusalem Talmud and their own older traditions. Yehudai argued that, as a result of Byzantine persecution, the Jews of Eretz Yisrael had only preserved Jewish tradition in a fragmentary and unreliable form.
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