A Babylonian amora of the fourth century, junior contemporary of Raba, and nephew of Aḥa b. Jacob. He is frequently quoted in halakic discussions by his contemporaries and successors, and received the title of Bar be-Rab (Fellow of the Academy) from his uncle Aḥa, with whom he carried on halakic controversies ('Er. 63a, Ket. 74a, Sanh. 42a, Naz. 42a).