Isma'il ibn Jafar

Isma'il ibn Ja'far was the eldest son of Ja'far al-Sadiq and the sixth Imam in Isma'ilism. He carried the epithet of al-Mubarak, on the basis of which one of the earliest Isma'ili groups became designated as the Mubarakiyya.

It seems likely that the Mubarakiyya were originally supporters of Isma'il before acknowledging Muhammad ibn Isma'il as their Imam. At any rate, Mubarakiyya was thus one of the original names of the nascent Isma'iliyya, a term coined by later heresiographers. A faction of the Mubarakiyya later developed into the Fatimid Isma'ilis, upholding the continuity of the Imamate in the progeny of al-Mubarak, acknowledging al-Mubarak himself as their sixth Imam. This enumeration was subsequently retained by the various branches of the Isma'ili.

A major crisis arose among the Shia after the death of Ja’far al-Sadiq, who had five sons. Abd Allah al-Aftah and Isma'il al-Mubarak were the eldest sons by his first wife Fatima, a granddaughter of Hasan Ibn Ali. Al-Mubarak was probably the second son of al-Sadiq. The exact date and circumstances of al-Mubarak's death also remain obscure. According to some Isma'ili authors, al-Mubarak survived al-Sadiq. Some sources, mainly Twelver texts, report that al-Mubarak died during the lifetime of al-Sadiq—but those same sources also report that al-Mubarak was seen several days later in Basra, suggesting that he did not really die but was sent away out of Medina.