Ja'far al-Sadiq (c. 702-765) was a great-great-grandson of the Prophet Muhammad, descended through both Husayn and, on his mother's side, from Abu Bakr. In Twelver Shia Islam he is the sixth Imam, and he is one of the rare early figures held in high honour across the sectarian divide.
He lived in Medina through the turbulent decades in which the Umayyad dynasty fell and the Abbasid rose, and he largely held himself apart from the revolts that convulsed the period, devoting himself instead to teaching. His circle in Medina was famous: the tradition credits him with thousands of students, and among those who are said to have studied with him or transmitted from him are Abu Hanifa and Malik ibn Anas, the eponyms of two of the four great Sunni schools of law. The saying attributed to Abu Hanifa, that he had never met anyone more learned than Ja'far, became a byword for the cross-sectarian esteem in which he was held.
His honorific, al-Sadiq, the truthful, marks that reputation. Much that is ascribed to him in later collections is difficult to verify at this distance, but the breadth of his renown as a teacher is not in doubt.