Iggeret of Rabbi Sherira Gaon (Hebrew: אגרת רב שרירא גאון), also known as the Letter of Rav Sherira Gaon, and the Epistle of Rav Sherira Gaon, is a responsum penned in the late 10th century (987 CE) in the Pumbedita Academy by Sherira ben Hanina, the Chief Rabbi and scholar of Babylonian Jewry, to Rabbi Jacob ben Nissim of Kairouan, in which he methodologically details the development of rabbinic literature, bringing down a chronological list of the Sages of Israel from the time of the compilation of the Mishnah, to the subsequent rabbinic works (Tosefta, Sifra, Sifre, etc.), spanning the period of the Tannaim, Amoraim, Savoraim, and Geonim under the Babylonian Exilarchs (Jewish Babylonian Aramaic: רֵאשׁ גלותאRēsh Galūthā), concluding with his own time. Therein, Sherira ben Hanina outlines the development of the Talmud, how it was used, its hermeneutic principles, and how its lessons are to be applied in daily life whenever one rabbinic source contradicts another rabbinic source. It is considered one of the classics in Jewish historiography.[1]