When he was 10 his family moved to Najaf where he studied various Islamic studies including Arabic language, rhetoric, logic, Islamic philosophy, the Hadith and Islamic jurisprudence, eventually studying under Grand Ayatollah Abu al-Qasim al-Khoei.
Born in a village in Ghazni Province, Afghanistan to Hazara parents, he holds Iranian and Afghani citizenships. His family were farmers and he started learning the Qur"an from the village cleric when he was five. When al-Khoei died in 1992 he supported Ali al-Sistani as the chair of the marjaiya in Najaf.
Under Saddam Hussein he adopted a quietist approach, avoiding politics and confrontation with the government.
Following the Invasion of Iraq by the United States and allies in 2003, al-Fayyad engaged more than any other marja with the occupying American and British military and diplomats, informing them of the views of the senior clerics. However, of all the marja"iyya Fayyad is reported to be the biggest opponent of the concept of the Guardianship of the Islamic Jurists.
However, this report is contradicted by the official website of the Shi"a Marja, wherein he remarks, "The correct opinion regarding the issue of "Vilayat-e-Faqih" (Guardianship of the Islamic Jurist) is that this issue requires no external proof, because the continuation of Islamic law, and its application, is dependent upon the continuation of the system of Vilayat". He continues, "The vilayat of the Prophet and the immaculate Imams, and in the time of the major occultation of the 12th Imam, the Islamic Jurist is bestowed with this vilayat.
lieutenant is unimaginable that Islamic Law could continue to exist without the continuation of this vilayat".
In 2007 press reports indicated that he was supervising the religious studies of the radical cleric Muqtada al-Sadr.
