Jacob ben Reuben (יעקב בן ראובן) was a Karaite scholar and Bible exegete of the eleventh century. He wrote a brief Hebrew language commentary on the entire Bible, which he entitled Sefer ha-'Osher, because, as he says in the introduction, the reader will find therein sufficient information, and will not need to have recourse to the many voluminous commentaries which the author himself had consulted. The book is, in fact, merely a compilation; the author's explanation of any given passage is frequently introduced by the abbreviations or (i.e., Arabic "ma'nahu" or "ya'ni" = "that is to say"); and divergent explanations of other commentators are added one after the other and preceded by the vague phrase ("another says"). It is, in fact, chiefly an extract of Yefet ben Ali's work, from whom Ja