Although originally political in nature, the differences between Sunni and Shia interpretations rapidly took on theological overtones. In principle, a Sunni approaches God directly: there is no clerical hierarchy. Some duly appointed religious figures, such as imams, however, exert considerable social and political power. Imams usually are men of importance in their communities, but they need not have any formal training. Committees of socially prominent worshipers usually are responsible for managing major mosque-owned lands. In most Arab countries, the administration of waqfs (religious endowments) has come under the influence of the state. Qadis (judges) and imams are appointed by the government.

The Muslim year has two religious festivals: Id al Adha, a sacrificial festival held on the tenth day of Dhu al Hijjah, the twelfth, or pilgrimage, month; and Id al Fitr, the festival of breaking the fast, which celebrates the end of Ramadan on the first day of Shawwal, the tenth month. To Sunnis these are the most important festivals of the year. Each lasts three or four days, during which time people put on their best clothes and visit, congratulate, and bestow gifts on each other. In addition, cemeteries are visited. Id al Fitr is celebrated more festively because it marks the end of Ramadan. Celebrations also take place, although less extensively, on the Prophet's birthday, which falls on the twelfth day of Rabi al Awwal, the third month.

With regard to legal matters, Sunni Islam has four orthodox schools that give different weight in legal opinions to prescriptions in the Quran, to the hadith, to the consensus of legal scholars, to analogy (to similar situations at the time of the Prophet), and to reason or opinion. Named for their founders, the earliest Muslim legal schools were those of Abd Allah Malik ibn Anas (ca. 715-95) and An Numan ibn Thabit Abu Hanifa (ca. 700-67). The Maliki school was centered in Medina, and the lawbook of Malik ibn Anas is the earliest surviving Muslim legal text, containing a systematic consensus of Medina legal opinions. The Hanafi school in Iraq stressed individual opinion in making legal decisions. Muhammad ibn Idris ash Shafii (767-820), a member of the tribe of Quraysh and a distant relative of the Prophet, studied under Malik ibn Anas in Medina. He followed a somewhat eclectic legal path, laying down the rules for analogy that were later adopted by other legal schools. The last of the four major Sunni legal schools, that of Ahmad ibn Muhammad ibn Hanbal (780-855), was centered in Baghdad. The Hanbali school, which became prominent in Arabia as a result of Wahhabi (see Glossary) influence, gave great emphasis to the hadith as a source of Muslim law but rejected innovations and rationalistic explanations of the Quran and the traditions (see Wahhabi Islam and the Gulf , this ch.).

Data as of January 1993