Jacob ben Reuben, who was active in the late eleventh century and the early part of the twelfth, was a Karaite scholar and biblical exegete from Byzantium. While traveling to spread his religious doctrines, he apparently collected Karaite Bible commentaries, especially those written in Judeo-Arabic. His most important work was the Sefer ha-ʿOsher (Book of Riches),a concise commentary in Hebrew, with Greek glosses, on the entire Bible. As Jacob explains in the introduction, the word “riches” in the title indicates that he drew from so many differ…