Yūdghān was the founder of one of the many Jewish sects in Babylonia and Persia around the beginning of the gaonic period. According to Jacob al-Qirqisānī (10th century), he was a student of Abū ʿĪsā of Isfahan, which indicates that he was active at the beginning of the Abbasid caliphate in the second half of the eighth century.

As is the case for the other Jewish sects of this era, our information about Yūdghān’s doctrines comes from Karaite and Muslim sources. His followers referred to him as the “shepherd,” meaning that they considered him the “shepherd of the nation.” According to the Kitāb …