Ja’far al- Sadiq, more formally named al- Sadiq Ja’far b. Muhammad b. ‘Ali b. al-Husayn and regarded by the Imami Shi’is as the sixth of their 12 imams, was born in Medina and spent virtually his entire life there. His father, Muhammad al- Baqir (d. 735), was a great- grandson of ‘Ali b. Abi Talib (d. 661), descended from Husayn b. ‘Ali (d. 680), while his mother was a descendant in the male line of the first caliph, Abu Bakr (d. 634). Ja’far took no part in the political upheavals of his day. When his paternal uncle Zayd b. ‘Ali (d. 740) rose against the Umayyads in 740, Ja’far refused to join him, and when Ja’far was offered the leadership of the Muslim community at the time of the Abbasid victory, he reportedly declined. In 762, he refrained from participating in the revolt against the Abbasid caliph Abu Ja’far al- Mansur (d. 775) that was led by another prominent ‘Alid, Muhammad al- Nafs al- Zakiyya (d. 762). Following the suppression of this revolt, Ja’far was summoned to the caliph’s court but was not harmed. He died three years later in Medina. Reports that he had been poisoned by order of Mansur are probably false. Disagreements as to who was to succeed him led to splits among his followers and marked the beginning of the Isma’ili sect.
As a scholar and traditionalist, Ja’far in his own lifetime was already held in high esteem and not only by Shi’is; both Abu Hanifa (d. 767) and Malik b. Anas (d. 795), the eponymous founders of the Hanafi and Maliki legal schools respectively, are said to have studied with him, and he often appears in chains of transmission in Sunni works of hadith. Non- Shi’is do not, however, regard him as an imam, but only as a distinguished jurist and transmitter. Deeply learned in religious law, Ja’far also is said to have been well versed in occult sciences such as astrology and alchemy. Various writings are ascribed to him, including a commentary on the Qur’an, though they are of dubious authenticity. Many of his Shi’i followers were residents of the city of Kufa, who would visit him during the pilgrimage.
Ja’far is often portrayed as playing a leading role in the growth of Imami law, known as “the Ja’fari legal school (madhhab).” Much of Imami law is based on countless utterances, directives, and decisions attributed to him (and in part to his father). These were set down by his disciples in written form.
The major components of the Imami doctrine of the imamate are said to have been in place by Ja’far’s time, and Ja’far (or some of his disciples) may well have been instrumental in giving them shape. At the center of the doctrine stands the principle of loyalty (walāya) to an imam who is a descendant of ‘Ali and his wife Fatima (the Prophet’s daughter). Adherence to this principle is considered a foundation of faith, and the Imami credo includes, in addition to the Sunni formula “There is no deity but God, and Muhammad is His messenger,” the declaration “‘Alī walī Allāh” (‘Ali is the beloved of God). The universe cannot exist without an imam. He is the axis of creation and the gate to God; recognition of the imam is a prerequisite for salvation. At a given moment, there can only be one active imam, though his successor may be at his side as a silent (ṣāmit) imam. ‘Ali’s appointment as the Prophet’s successor was announced on various occasions, most significantly at Ghadir Khumm, during Muhammad’s return to Medina from his last pilgrimage. ‘Ali’s rights were usurped by the first three caliphs, who are therefore regarded as sinners; so too are those among the Prophet’s companions who supported these caliphs. The imamate passed from ‘Ali via his son Hasan to Hasan’s younger brother Husayn and is handed down among descendants of the latter. The identity of the imams is divinely determined and is confirmed by both explicit designation (naṣṣ) and the testament (waṣiyya) of the previous imam (or, in ‘Ali’s case, of the Prophet). The imams’ position of leadership is also based on their unique characteristics, notably their possession of special knowledge (‘ilm). This knowledge derives from four major sources: oral transmission from one imam to the next, transmission by heredity, transmission by inspiration, and sacred books that are unknown to ordinary mortals. The sources offer differing descriptions of the nature and extent of the imam’s knowledge: according to some accounts, the imam has perfect mastery of the Qur’an and hadith. Elsewhere, he is also said to be endowed with supernatural knowledge (such as knowledge of the future and of all languages) and an understanding of the esoteric meaning of the Prophet’s teaching. There is general agreement that the imam is divinely protected against error (ma’ṣūm) and is thus an infallible guide to Islamic law and doctrine.
The belief that Muhammad was the seal (i.e., the last) of the prophets is common to Imamis and Sunnis; but in contrast to the latter, the Imamis in their law give the imam a status identical to that of the Prophet. In other words, while both Sunnis and Imamis regard the Prophet’s utterances and actions as the second source of Islamic law (after the Qur’an), the Imamis add to this source the utterances and actions of the imams. In fact, the number of sayings in Imami literature attributed to the various imams, and especially to Ja’far, exceeds by far the number of sayings attributed to the Prophet.