According to Shi’ite tradition, the Twelve Imams, descendants of the Prophet Muhammad’s cousin and son-in-law Ali Ibn Abi Talib, were endowed with divine qualities that enabled them to lead the Shi’ite believers and to function as Allah’s emissaries on earth. However, when the Twelfth Imam Muhammad Al-Mahdi* disappeared in 941 CE, his connection with the Shi’ite believers was severed, and since then, the Shi’ites are commanded to await his return at any time.
In the meantime, Shi’ite senior clerics are considered to be the representatives of the Imams, and thus have the authority to handle the affairs of the Shi’ite community, mainly in the religious and judicial spheres, until the Hidden Imam returns to lead the Shi’ite community and deliver it from its suffering.
According to Shi’ite belief, during the period of the Mahdi’s absence (termed ghaibat or “occultation”), no one but God knows the hour of the Mahdi’s return, and no man can presume to foresee when this hour will come. Upon the Mahdi’s reappearance, all wrongs will be righted, divine justice will be instated, and the truth of Shi’ite Islam will be acknowledged by the entire world.
*The Twelfth Imam, the Shi’ite messiah, is also called Muhammad Al-Muntazar (“the expected”), Imam Al- Zaman (“The Imam of the Age”) and “the Hidden Imam.”