Belief in Imam Mahdi (AJ) has deep roots in the Quran, the traditions of the Prophet Muhammad (PBUH), and the sayings of the Ahl al-Bayt (AS). Authoritative Shiite sources such as Kamal al-Din, Al-Ghaybah (by Sheikh Tusi and Al-Nu‘mani), and Bihar al-Anwar extensively discuss Mahdism and present it as a fundamental tenet of faith.