Iggeret of Rabbi Sherira Gaon (), 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 Gaon, 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, Sifrei, etc.), spanning the period of the Tannaim, Amoraim, Savoraim, and Geonim under the Babylonian Exilarchs (Resh Galutha), concluding with his own time. Therein, Sherira Gaon 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. Letter's content Sherira's letter (henceforth: Iggeret), in its length, takes the form of a short book. In it, Sherrira endeavored to answer an inquiry from Kairouan about the authorship and composition of the Mishnah and Talmud, and in particular why earlier authorities are seldom cited by name and the authorities that are so cited do not seem to be chronologically continuous. Sherira is one of the first to present a detailed discussion on the Savoraim, including their activity in revising and finishing the Talmud. The letter he wrote is the chief source for the history of the Talmudic, post-Talmudic, and geonic periods. Jacob ben Nissim of Kairouan addressed, in the name of his community, a number of questions of historical interest to Sherira, inquiring especially into the origin of the Mishnah and the sequence of the redactions, the origin of the Tosefta, and the sequence of the Talmudic, post-Talmudic, and geonic authorities. The reply seeks to clarify the basic principles upon which the chain of transmission of the Oral Law is founded. Sherira clearly and lucidly answers all these questions, throwing light upon many obscure passages of Jewish history. This historical responsum, which is composed half in Aramaic and half in Hebrew, reveals Sherira as a true chronicler, with all the dryness and accuracy of such a writer, though his opinions on the princes of the Exile belonging to the branch of Bostanai, as well as on some of his contemporaries,