Jaʿfar ibn Muḥammad aṣ-Ṣādiq (Arabic: جَعْفَر ٱبْن مُحَمَّد ٱلصَّادِق; 700 or 702–765 CE), commonly known as Ja’far al-Ṣādiq or simply as-Sadiq (The Truthful), was an 8th-century Muslim scholar and scientist. He is considered as an Imam by Twelver and Isma’ili Shī’ites, and a major figure in the Hanafi and Maliki schools of Sunni jurisprudence. He was a descendant of the Caliph Ali and Fatimah bint Muhammad on the side of his father, Muhammad al-Baqir, and of Muhammad ibn Abu Bakr on the maternal side of his family, Umm Farwah bint al-Qasim. Muhammad ibn Abu Bakr was raised by Ali, but was not his son. Ali used to say: “Muhammad Ibn Abu Bakr is my son but from Abu Bakr’s lineage”. Al-Sadiq is the 6th Imam for Twelvers, is recognized by the majority of the Shi’ite sects as an Imam, and is revered in traditional Sunni Islam as a transmitter of Ahadith, therefore a prominent jurist, and a mystic to Sufis. Despite his wide-ranging attributions in a number religious disciplines, no works penned by Ja’far himself remain extant.
Al-Sadiq was born in either 700 or 702 CE. He inherited the position of imam from his father in his mid-thirties. As a Shi’ite Imam, al-Sadiq stayed out of the political conflicts that embroiled the region, evading the many requests for support that he received from rebels. He was the victim of some harassment by the Abbasid caliphs, and was eventually, according to most Shi’ite Muslims, poisoned at the orders of the Caliph Al-Mansur. In addition to his connection with Sunni schools of Sunni jurisprudence, he was a significant figure in the formulation of Shia doctrine. The traditions recorded from al-Sadiq are said to be more numerous than all hadiths recorded from all other Shia imams combined. As the founder of “Ja’fari jurisprudence“, al-Sadiq also elaborated the doctrine of Nass (divinely inspired designation of each imam by the previous imam), and Ismah (the infallibility of the imams), as well as that of Taqiyyah.