Sepher Mechilta [Halachic Midrash to the Book of Exodus]. Anonymous (Attributed to the Mishnaic Sage, Rabbi Yishmael).

Although it was commonly accepted that the opposing schools of Rabbi Yishmael and Rabbi Akiva composed different sets of Halachic Midrashim, this present collection is the only one known to exist until the discoveries of additional texts in the 19th century. R. Nissim ben Jacob, R. Samuel HaNagid and Maimonides have all identified R. Yishmael as the author of this Sepher Mechilta. Such authorship is indeed recognized by many in the scholarly community as plausible, but contingent upon the acknowledgment that the work underwent a subsequent process of revision following its initial composition. Over the past century-and-a-half, fragments of a variant Mechilta texts were discovered in the Cairo Genizah and were studied, first by Rabbi David Tzvi Hoffman of Berlin and later by Professors J.N. Epstein and E.Z. Melamed of Jerusalem. It was initially believed that these fragments simply represented a variant text to Rabbi Yishmael’s Mechilta, but have by now been positively identified as belonging to the lost Mechilta d’Rebbi Shimon bar Yochai, a student of Rabbi Akiva. The Genizah fragments were joined with various citations preserved by the Yemenite Midrash HaGadol in order to artificially reconstruct and restore the original Mechilta d’RaShB”I - an extraordinary scholarly accomplishment. Still debated today is whether additional discovered fragments prove the existence of a third Mechilta - the Mechilta d’Rebbi Yishmael on the Book of Devarim. In any event, the present work is the Mechilta anthology that did indeed survive the travails of history, and this Constantinople text, the first printed appearance of the Mechilta, is a significant milestone in its preservation.