Musa ibn Ja'far al-Kazim (Arabic: مُوسَىٰ ٱبْن جَعْفَر ٱلْكَاظِم, romanized: Mūsā ibn Jaʿfar al-Kāẓim; 745–799) was a descendant of the Islamic prophet Muhammad and the seventh Imam in Twelver Shia Islam, succeeding his father Ja'far al-Sadiq and preceding his son Ali al-Rida. Born around 745 in Medina, al-Kazim spent the first twenty years of his life under the care and guidance of his father. This period coincided with the power struggle between the Abbasids and the Umayyads. Following Ja'far al-Sadiq's death, a minority of his followers recognized his other son Isma'il ibn Ja'far as the next Imam, separating from the mainstream Shia Islam and forming the Isma'ili sect. However, Musa al-Kazim attracted the largest following, and his followers ultimately became what developed into Twelver Shia Islam, the largest branch. His Imamate spanned the reigns of the Abbasid caliphs al-Mansur, al-Mahdi, al-Hadi, and Harun al-Rashid. Like his predecessors, al-Kazim avoided politics and devoted himself to religious teachings. He was nevertheless tightly restricted by the Abbasid caliphs and spent much of his adult life in their prisons. To counter these harsh restrictions, he established the network of representatives (Wokala) to organize the affairs of his followers across the Islamic word.
The numerous Alid revolts further increased the caliphs' suspicions, and al-Kazim's final imprisonment ended with his death in prison around 799 in Baghdad, for which Harun al-Rashid has been widely regarded as primarily responsible. After al-Kazim's death, some of his followers refused to accept that he had died, believing that he was the Mahdi who had entered occultation and would return. This sect, known as the Waqifite, disappeared over the decades that followed. Al-Kazim played a key role in eradicating extreme views and exaggerations (ghuluww) from Shia Islam. His answers to legal questions have survived in Wasiyya fi al-aql, and he is credited with numerous supplications. Al-Kazim is also revered for his piety in Sunni Islam, and considered a reliable transmitter of prophetic sayings. He is a link in the initiatic Golden Chain in Sufism, and some Sufi saints are associated with him. Various nonprophetic miracles are attributed to al-Kazim, often emphasizing his precognition. Al-Kazim had numerous children, the most famous of whom being Ali al-Rida, his successor and the eighth Imam. Today, Musawi Sayyids, who trace their lineage to Musa al-Kazim, are among the most numerous and widespread Sayyid lineages, due to the large number of children he had. The Al-Kazim Shrine in Baghdad, Iraq, where his grandson and the ninth Imam Muhammad al-Jawad is also buried, is a holy site in Shia Islam.
Musa was probably born on 8 November 745 (7 Safar 128 AH). He was born either in Medina, or in nearby al-Abwa', located between Medina and Mecca. Alternative birth dates are September 745 and 746–747. His father was Ja'far al-Sadiq, a descendant of Ali ibn Abi Talib and Fatima, who were the cousin and daughter of the Islamic prophet Muhammad, respectively. Ja'far al-Sadiq was widely accepted as the legitimate imam by the early Shia community, who rejected the ruling Umayyad caliphs as usurpers. Musa's mother was Hamida Khatun, a Berber slave-girl. She was also known as al-Musaffat (lit. 'the purified'), a title which was perhaps a reference to her religious learning, as she is said to have taught Islamic jurisprudence to women in a seminary in Medina. Abdallah al-Aftah and Isma'il ibn Ja'far were the elder half-brothers of Musa, and Muhammad ibn Ja'far al-Sadiq was his younger full brother. Musa was about four years old when the Abbasid revolution overthrew the Umayyad Caliphate in 750. He continued to live in Medina under the authority of his father al-Sadiq, until the latter died in 765. Ja'far al-Sadiq was poisoned at the instigation of the Abbasid caliph al-Mansur (r. 754–775), according to the Shia.
After the death of al-Sadiq, Musa al-Kazim remained in Medina, where he stayed out of politics, similar to most of his predecessors. As with his father, al-Kazim instead taught religious sciences in Medina. Over time, he also established an underground network of representatives (wukala) to collect religious donations from his followers and organise their affairs.
The Abbasids, who claimed descent from Muhammad's uncle Abbas ibn Abd al-Muttalib, had rallied the support of the Shia community against the Umayyads in the name of the family of Muhammad. But many Shias were disillusioned when the Abbasid al-Saffah (r. 750–754) declared himself caliph, as they had instead hoped for an Alid leader, one who had descended from Muhammad, that is, a descendant of his daughter Fatima and Ali ibn Abi Talib. The Abbasids soon turned against their former allies, and were generally hostile to the Shia imams, especially after the abortive 762–763 revolt of the Alid pretender Muhammad al-Nafs al-Zakiyya. Musa al-Kazim was contemporary with the Abbasid caliphs al-Mansur, al-Hadi, al-Mahdi, and Harun al-Rashid. Unlike his father, who often taught freely in Medina, al-Kazim was highly restricted by the caliphs, and spent much of his adult life in the Abbasid prisons in Iraq. By one Shia account, under the Abbasids' watchful eyes, al-Kazim even discouraged his followers from greeting him in public.
Reign of al-Mansur (r. 754–775)
Shia sources blame the Abbasid caliph al-Mansur for the death of Ja'far al-Sadiq, who did not publicly designate an heir, likely fearing the Abbasid reaction. Shia sources report that the caliph ordered his governor of Medina to kill the heir to al-Sadiq, a plan that was thwarted when the governor found out that al-Sadiq had appointed four or five legatees. The resulting crisis of succession to al-Sadiq was ultimately resolved in favor of al-Kazim, who spent the first ten years of his imamate under al-Mansur. This succession crisis nevertheless weakened the mainstream Shia, which is perhaps why al-Mansur left al-Kazim relatively unmolested, while still keeping him under surveillance. This initial mild treatment of al-Kazim would not continue under future caliphs.
Reign of al-Mahdi (r. 775–785)
During the ten years of the reign of al-Mahdi, al-Kazim remained under surveillance in Medina. He was arrested at least once by the caliph, who around 780 briefly imprisoned him in the Abbasid capital of Baghdad. There Musa was placed in the custody of the prefect of police, al-Musayyab ibn Zuhayr al-Dabbi, who later became a follower of al-Kazim. According to the Sunni historian al-Tabari (d. 923), al-Mahdi had a dream in which Ali ibn Abi Talib berated him for imprisoning his progeny, which apparently compelled the caliph to set al-Kazim free, after he pledged not to revolt against the caliph.
Reign of Musa al-Hadi (r. 785–786)
Musa al-Kazim did not lend his support to the 786 revolt of the Alid pretender al-Husayn ibn Ali al-Abid, and a letter attributed to al-Kazim even warns al-Husayn about his violent death. The Shia imam was nevertheless accused of complicity by the Abbasid caliph al-Hadi, who was dissuaded from killing al-Kazim only by the intervention of the judge Abu Yusuf. The caliph died soon after, and thus al-Kazim survived. He then composed the supplication Jawshan Sagheer (lit. 'coat of mail') in gratitude, according to the Shia jurist Sayyed Ibn Tawus (d. 1266).
Reign of Harun al-Rashid (r. 786–809)
The persecution of the Shia reached a climax during the caliphate of Harun, who is said to have killed hundreds of Alids. Harun also arrested al-Kazim, brought him to Baghdad, and was apparently intent on killing him but then set him free as a result of a dream, it is said. Harun was perhaps provoked by an earlier incident, according to the Sunni historian Ibn Khallikan (d. 1282): When the two men visited the tomb of Muhammad in Medina, Harun, intent on showing his family ties to the prophet, had said, "Salutation unto thee, O prophet of God, unto thee who art my cousin!" Musa al-Kazim apparently countered with, "Salutation unto thee, O my dear father!" This angered Harun, who retorted, "O Abu al-Hasan [al-Kazim], such glory as thine is truly to be vaunted of!"