Yefet ben Ali (Hebrew: יפת בן עלי הלוי) was perhaps the foremost Karaite commentator on the Bible, during the "Golden Age of Karaism". He lived during the 10th century, a native of Basra ( in present-day Iraq) Later in his life, he moved to Jerusalem, between 950 and 980, where he died. The Karaites distinguished him by the epithet maskil ha-Golah (teacher of the Exile).
His commentaries were written in Arabic, and covered the entire Tanakh. They were accompanied by a very literal translation of the Hebrew text, which often violated the rules of Arabic grammar. These writings influenced the rabbinical sage Abraham ibn Ezra, who quotes Yefet forty-two times in his commentary of the minor prophets.
Unlike his Karaite predecessors in the field of Bible exegesis, Yefet realized the importance of grammar and lexicography for the interpretation of Scripture, although he did not excel in either. The interest which his commentaries present lies chiefly in the accumulation of material for the history of the differences between traditional Judaism and the Karaites; for he enters into lengthy disputes with traditional rabbis, especially with Saadia, from whose commentaries on the Bible and polemical works, including some no longer in existence, he gives many extracts. Thus in regard to Ex. xxxv. 3 he discusses with Saadia the kindling of a fire by a non-Jew on Sabbath, a practise which the Karaites considered to be forbidden. Yefet reproaches Saadia with being unfaithful to the principles he himself had laid down for the interpretation of the Law, according to which no deductions by analogy are admissible in definite revealed precepts. On Lev. xxiii. 5 Yefet cites fragments from Saadia's "Kitab al-Tamyiz", a polemical work against Karaism, in which the author states that there are three sects which are divided on the question of the new moon: (1) the Rabbinites, who, except in special cases, determine it by the molad; (2) the sect of the Tiflis, which follow the molad absolutely; and (3) a sect which is guided by the first appearance of the moon.
Yefet claims full freedom for the exegete, refusing to admit any authority for the interpretation of the Law; and, although he sometimes uses the thirteen hermeneutic rules laid down in the Mishnah, he denies their authority: they are to be applied, he claims, only when it is not possible to explain the passage literally. Thus, notwithstanding his veneration for Anan ben David, the founder of Karaism, and for Benjamin Nahawandi, he often rejects their interpretations.