Abū ʿĪsā al-Iṣfahānī, Isḥāq b. Yaʿqūb, was the leader of the Jewish sect of the ʿĪsawiyya or Iṣfahāniyya in Persia during the late Umayyad and early ʿAbbāsid era. He was killed in Rayy in the reign of the caliph al-Manṣūr.

His name is given as either Muḥammad b. ʿĪsā (Ibn Ḥazm, 1/179), or Abū Isḥāq b. Yūsuf (Abū al-Maʿālī, 57). He was also called ‘Oved Elohim’, meaning ‘worshipper of God’ in Hebrew (al-Shahrastānī, 2/20). He came from Naṣībīn and was a tailor by profession. His followers maintained that he was uneducated (ummī) and that his books were written through pure inspiration …