Jacob ben Nissim ibn Shahin יעקב בן נסים אבן שאהין

He headed the beit midrash of Kairouan and was the man through whom the communities of North Africa dealt with the Babylonian academies, gathering questions and forwarding them to Sura and Pumbedita.

One of those questions mattered more than the rest. The Kairouan community asked how the Mishnah and the Talmud had taken shape, why the early authorities are so seldom named, and why the chain of transmission shows gaps. The answer came in 987 and is known as the Epistle of Rav Sherira Gaon—the letter from which we know the succession of generations from the Tannaim to the Geonim.

Of Jacob ben Nissim himself little is known. No reference work gives his dates. His son was Rav Nissim Gaon, who headed the Kairouan academy after him.

An Arabic commentary on Sefer Yetzirah was ascribed to him, but the Encyclopaedia Judaica disagrees: it rests on a text of Isaac Israeli and was apparently written by Dunash ibn Tamim. A word on the dates as well: the same encyclopaedia prints his death as "1106/07", which is impossible—Sherira's letter reached him in 987 and his son died in 1062; it is almost certainly a misprint for 1006/07. We do not substitute a date of our own.