As the young community grew and established itself in Medina, it became increasingly necessary for Muhammad to address countless questions of order and acceptable practice. Some of the later texts of the Qur’an deal with specific issues, such as how to pray, what foods and activities to avoid, and how to observe basic social relationships. After Muhammad died and the Arab armies expanded into new territories and encountered new cultures and religious communities, the Muslims had to confront countless problems previously unknown: How would they deal with issues that neither the Qur’an nor the Hadith addressed?

Local Muslim leaders often had to improvise, exercising their best personal judgment and acting as they believed Muhammad would have done. They strove to perpetuate the Prophet’s example, his sunna. But authorities and leading scholars in Medina, and later in other cities, looked for ways to standardize the procedure of extending the application of the Qur’an and Hadith to changing circumstances. They gradually agreed that one could solve problems not treated directly in the Qur’an and Hadith by appealing to the “actual practice” of the local community or to the “consensus” (ijma’, pronounced ijMAA) of legal scholars. But since some questions were too new for any consensus to have developed, scholars agreed that one could apply a form of “reasoning by analogy” (qiyas, pronounced keeYAAS) that followed strict rules so as to keep the process as free of personal whim as possible. Leading legal scholars in different cities devised slightly different formulas for using the four “roots” of the law (Qur’an, Hadith, Consensus, and Analogical Reasoning), some allowing greater latitude in appealing to the third and fourth roots. Four legal methodologies dominant among Sunni Muslims came to be called the “schools” (madhhabs), while several other distinctively Shi’a schools eventually developed as well.