Arwa al-Sulayhi
According to Ismā'īlī [Musta'ali Tayyabī] tradition, before the 21st Fatimid [Musta'ali] Imam, Taiyab abi al-Qasim went into state of occultation from Cairo in 528 AH/1134 AD, his father, the 20th Imām al-Amīr had instructed Queen Arwa al-Sulayhi/Al-Hurra Al-Malika in Yemen to anoint a vicegerent after the occultation of his son al-Tayyib Abu'l-Qasim. Queen Arwa trained and appointed Syedna Zoeb bin Moosa as the first Da'i in the modern office.