Abu'l-Fawaris Ahmad ibn Ya'qub was an early 11th-century Isma'ili scholar and missionary (da'i) active in Syria, which at the time was largely under the rule of the Fatimid Caliphate.
[1] Abu'l-Fawaris was active in the reign of the Fatimid imam-caliph al-Hakim (r. 996–1021),[2] and a contemporary of the fellow Isma'ili scholars, Ahmad ibn Ibrahim al-Naysaburi and Hamid al-Din al-Kirmani.
All three elaborated Isma'ili ideas about the Imamate, apparently independently, since they do not cite each other's works.
[2] In it, Abu'l-Fawaris argues about the existence of the imamate as a necessity, as the Quran, the sharia (the body of Islamic law) and the sunnah (the traditions ascribed to Muhammad) are not sufficient.
[2] The treatise has been published in a critical edition with English translation by Sami N. Makarem as The Political Doctrine of the Ismāʿīlīs: The Imamate.