Abu ‘Abdu’llah Ja’far ibn Muhammad known by the title as-Sadiq (the truthful) was the eldest son of Muhammad al-Baqir, while his mother was a great-granddaughter of the first Caliph, Abu Bakr. His date of birth is variously given as 80/669, 83/702 or 86/705. He was therefore about thirty-seven years old when his father died.

Apart from the First Imam ‘Ali, no other Imam of the Twelver line achieved as great a renown in the Muslim world for piety and learning as Ja’far as-Sadiq did in his own lifetime. Many of those who sat in as-Sadiq’s circle of students later went on to become renowned scholars and jurists. Abu Hanifa, the founder of the Hanafi School of Law in Sunni Islam, is said to have been one of his students, and Malik ibn Anas, the founder of Maliki School of Law, was also evidently closely associated with as-sadiq and transmitted Traditions from him. However, it must not be imagined that more than a few of the thousands of students who are reported to have studied under as-Sadiq were Shi’is or accepted his claim to be Imamate. Indeed, it cannot be certain that he openly advanced such a claim.

During as-Sadiq’s Imamate there were stirring events throughout the Mislim world. The Shi’a of this time appear to have been desperately looking for any ‘Alid (descendant of ‘Ali) who could establish his authority and take over the Caliphate. Thus they supported, in turn: Zayd’s revolt in 122/740; the rebellion of ‘Abbdul’llah ibn Mu’awiya (a descendant of Ja’far, ‘Ali’s brother) in 127/744; the ‘Abassid rising beginning in 129/747, which received a great deal of Shi’i support, at least while the real purpose of the rising was concealed under the claim to be acting for ‘one who shall be chosen from the family of the Prophet’; and the revolt of Muhammad an-Nafs az-Zakyya 9the pure soul) in 145/762 against the ‘Abbasids. Throughout all these turbulent events, as-Sadiq followed the policy of his father and grandfather and remained politically quietists. Even when Abu Salama, the political leader of the ‘Abassid revolt, reportedly offered him the Caliphate, as-Sadiq declined it.

The Imamate of as-Sadiq may be said to consist of two parts. During the first part, while the Umayyads were in power, as-Sadiq taught quietly in Medina and succeded in establishing his considerable reputation. During this phase he was relatively free from molestation by the authorities. Once the ‘Abbasids came to power, and particularly during the reign of the second ‘Abassid Caliph, al-Mansur, as-Sadiq began to be harrased. On the several occasions he was summoned to Kufa and held in prison, and Shi’s historians describe several attempts by al-Mansur to kill him. Husain Jafri has suggested that it was under as-Sadiq that the doctrine of nass (designation of the Imam by the preceding Imam) as an essential pre-requisite for the Imamate, and the doctrine of ‘ilm (the special knowledge of the Imam), were fully developed. This may well have been so, for there was certainly a profusion of claims and counter-claims at this time and it was the doctrine of nass that both distinguished the Twelver line from other ‘Alid claimants and also provided the justification for the quietists line taken by these Imams. The doctrine of taqiyya (religious dissimulation) was also developed at this time. It served to protect the followers of as-Sadiq at a time when al-Mansur was conducting a brutally repressive campaign against ‘Alids and their supporters.

Most authorities agree that as-Sadiq died in 148/765. As usual, Shi’i historians have attributed his death to poisoning, on this occasion by the Caliph al-Mansur.

Bibliography:
See M. Momen, An Introduction to Shii Islam (1985).