[15] Immediately after the death of al-Askari in 260 (874),[16] Uthman ibn Sa'id (d. 880) claimed that the eleventh Imam had a young son, named Muhammad, who had entered a state of occultation (ghayba) due to the Abbasid threat to his life.
[19] Twelver sources detail that Muhammad al-Mahdi made his only public appearance to lead the funeral prayer for his father instead of his uncle, Ja'far.
[20][21] Thus began a period of about seventy years, later termed the Minor Occultation (al-ghaybat al-sughra, 260-329 AH, 874–940 CE), during which it is believed that four successive agents represented the Hidden Imam,[22] collectively known as the Four Deputies (al-nuwwab al-arba').
Tusi in his Rijal reports that the eleventh Imam had appointed Abu Ja'far and his father as agents of his son, Muhammad, in the presence of a group of Yemeni followers.
[26] Abu Ja'far, who served for some forty years in this office, has been credited with the unification of the mainstream Shia behind the son of al-Askari as the twelfth Imam in concealment.