Sunni and Shia Islam

The Prophet Muhammad died in Medina in 632 without, in the Sunni understanding, naming a successor. A gathering of leading Muslims at a covered meeting place known as the Saqifa chose his close companion and father-in-law Abu Bakr as caliph, “successor”, to lead the community. Abu Bakr was followed by Umar and Uthman, and in 656 by Ali ibn Abi Talib, the Prophet’s cousin and the husband of his daughter Fatima. Sunnis honour these four as the “rightly guided” caliphs.

Shia Muslims remember the same events differently. They hold that the Prophet had designated Ali as his successor, above all at Ghadir Khumm on the way back from his final pilgrimage, when he declared, in words both traditions record, “For whomever I am his master, Ali is his master.” Sunnis read the saying as a statement of love and honour for Ali; Shia Muslims read it as an appointment. For them, the choice of Abu Bakr set aside the rightful leader.

Ali’s caliphate was marked by civil war, and he was assassinated in 661. Power passed to the Umayyad dynasty. In 680 Ali’s son Husayn, the Prophet’s grandson, refused allegiance to the caliph Yazid and was killed with members of his family and companions at Karbala, in present-day Iraq. Karbala became the central memory of Shia faith, a story of martyrdom, loyalty and resistance to injustice.

The two traditions did not crystallise at once. Over the next three centuries, scholars on each side gathered hadith, built schools of law and set out theology. By the tenth century, Sunni and Shia Islam had become recognisably distinct traditions with their own institutions.

The deepest difference concerns authority after the Prophet. For Sunnis, religious guidance rests on the Quran and the Prophet’s sunnasunna The example of the Prophet Muhammad, in his words and actions, recorded in the hadith. Glossary, his example as recorded in hadith, interpreted by the consensus of scholars. No later leader shares the Prophet’s special status. For Twelver Shia, the largest Shia branch, God provided the community with twelve imams from the Prophet’s family, beginning with Ali, who were free from sin and divinely guided. The twelfth imam, Muhammad al-Mahdi, is believed to have gone into hiding in the ninth century and will return at the end of time to establish justice.

These views shape how each tradition reads its sources. Sunnis rely especially on six canonical hadith collections, the most respected being those of al-Bukhari and Muslim. Shia Muslims place most trust in reports transmitted through the imams and use four main books, the first of which is al-Kulayni’s al-Kafi. In law, Sunnis follow one of four schools, which recognise one another as valid, while most Shia follow the Ja‘fari school. Shia scholars give a wide role to reasoned interpretation, ijtihad, and believers usually choose a living senior scholar, a marja‘ al-taqlid, whose rulings they follow.

In daily practice the two are close. Both pray the same five prayers, though Shia Muslims often combine them into three sessions and place their foreheads on a small tablet of clay, often from Karbala. Both fast in Ramadan and make the pilgrimage to Mecca. Shia Muslims also visit the shrines of the imams at Najaf, Karbala, Mashhad and elsewhere. The month of Muharram, and above all Ashura, is a time of mourning for Husayn, with sermons, processions and passion plays. Twelver law also permits a fixed-term marriage, mut‘a, which Sunni schools do not accept.

Theology shows similar overlap and difference. Most Sunnis follow the Ash‘ari or Maturidi schools of theology, while others keep to a more literal creed associated with Ahmad ibn Hanbal. Twelver Shia theology lists five “roots of religion”: the oneness of God, divine justice, prophethood, the imamate and the resurrection. Shia scholars drew on rational theology, holding that God’s justice can be grasped by reason, a position close to that of the earlier Mu‘tazila. Mystical paths cross the boundary: Sufi orders are found mainly among Sunnis, yet most of them trace their spiritual chains back to Ali, and Shia tradition has its own strong current of mystical philosophy.

Standard estimates, such as those of the Pew Research Center, put Sunnis at about 85–90% of the world’s Muslims and Shia at about 10–13%. Sunnis are the majority across most of the Muslim world, from Morocco and Egypt to Turkey, Indonesia and Bangladesh. Shia Muslims are the majority in Iran, Iraq, Azerbaijan and Bahrain, and form large communities in Lebanon, Pakistan, India, Afghanistan, Yemen, Saudi Arabia and Kuwait. A third, smaller branch, the Ibadis, is found chiefly in Oman.

The Shia themselves are diverse. Twelvers form the large majority. Ismailis, who follow a different line of imams after the sixth imam, Ja‘far al-Sadiq, include the Nizari community led by the Aga Khan. Zaydis, found chiefly in Yemen, recognise a different fifth imam and are in law and practice close to Sunnis. Shia history has also known powerful dynasties: the Ismaili Fatimids, who founded Cairo in the tenth century, and the Safavids, who made Twelver Shi‘ism the official faith of Iran from 1501.

Relations between the two traditions have varied greatly across history and place. In many cities Sunnis and Shia have lived as neighbours, studied with the same teachers and married one another. Scholars on both sides have also worked for mutual recognition: in 1959 Mahmud Shaltut, head of al-Azhar in Cairo, declared it permissible to follow the Ja‘fari school, and the Amman Message of 2004–2005 affirmed that the Sunni and Shia schools of law all belong to Islam. In recent decades, rivalries between states and conflicts in the Middle East have at times been framed in sectarian terms, though historians stress that the causes are largely political.