زيد بن علي
In the context of the Shi'a belief in spiritual leadership or Imamate, Zaydis believe that the leader of the Ummah or Muslim community must be "Fatimids": descendants of Muhammad through his only surviving daughter Fatimah, whose sons were Hasan ibn ʻAlī and Husayn ibn ʻAlī. These Shi'a called themselves Zaydi to differentiate themselves from other Shias who refused to take up arms with Zayd ibn Ali.