The Isma'ilite sect comes into being after the death in 765 of Ja'far ibn Muhammad, the sixth imam, or spiritual successor to the Prophet, who is recognized by the Shi'ites.

The term imam imam is used in the Koran to mean leader, guide, model, or sign, and, for Shiites, meaning only a descendant from Ali, the son-in-law of Muhammad.

Most Shiites acknowledge Ja'far's younger son, Musa al-Kazim, as the seventh imam and will acknowledge his successors through the twelfth imam: these will become known as the Ithna 'Ashariyah, or Twelvers, the largest and most conservative of the Shi'ite sects.

Those who support his older, disinherited son, Ismail, become known as Ismailis; also Sabiyah, or Seveners, as they recognize Ismail as the seventh and last imam until the return of his son at the end of time.