The Prophet Muhammad was the interpreter of religious doctrine par excellence for the Muslim community. In the centuries after the Prophet’s death, Muslim rule extended from Spain to the borders of China, and some thought that these rulers had abandoned the ideals of Muhammad’s community at Medina. During the life of the Prophet, people began to collect aḥadīth (pl. of ḥadīth), the sayings of the Prophet as transmitted by his companions. Ḥadīth collections form an important part of the Sunnah, the example of the Prophet. Many critics of Muslim rulers were authorities on the Sunnah and respected interpreters of the Quran. These learned persons, collectively called the ‘ulamā’, derived legal interpretations [fiqh] from the divine plan for humans known as sharī‘ah. If sharī‘ah is the totality of God’s will regarding human action as represented in the Quran and Sunnah, then fiqh is the human endeavor to interpret it. Muslims, seeking to follow God’s will in accordance with the example of the Prophet, look to these interpretations in order to best understand how to prepare for and perform devotional acts, regulate marriage and business contracts, and care for the poor. Contrary to popular perceptions of Islamic law, only a small percentage addresses criminal law; the vast majority of fiqh is related to ritual law and devotional practice. 
The legal methods and rulings of leading Sunni ‘ulamā’ came to act as precedents for the community of scholars and judges, and there gradually developed a number of accepted schools of interpretation of the sharī‘ah, of which four in the Sunni world remain. Named after the great scholars whose legal precedents they take after, they are the Ḥanafī, Mālikī, Shāfi‘ī, and Ḥanbalī schools. The basic sources of fiqh are the Quran, the Sunnah, ijmā’ [the consensus of the community], and qiyās, or reasoning by analogy. The Shi‘a developed their own schools of interpretation, the most prominent of which is the Ja‘farī school. The Quran and Sunnah, as interpreted by their Imams, are important sources for their fiqh. In addition, they emphasize ‘aql, or intellect, as a source.
Islamic law was never a static set of universally applied legal declarations. It is always culturally and historically interpreted and “proper” interpretation is itself often debated within and among Muslim communities across the globe. For example, in many parts of the Ottoman Empire Christians and Jews often chose to use Islamic courts to adjudicate domestic disputes because they believed they would get a fairer hearing there than they might through the alternative legal systems available. Diverse legal opinions and perspectives were one factor that contributed to the spread of Islam, as well as its adaptiveness among divergent cultures.
In contemporary times, Islamic law continues to shape the devotional lives of many Muslims and regulate marriage, divorce, banking and other social and business contracts. In some countries, it has been interpreted as a rigid set of religious laws that serves as an influence within the national legal system or operates as an independent, parallel court system, and in some contexts it has been problematically adopted and imposed by non-state actors. Ultimately, it remains diverse and sometimes greatly contested. For example, some women and men in Saudi Arabia challenge interpretations of the sharī‘ah that have been codified as laws barring women from driving cars. Most Muslims decry the interpretation of the sharī‘ah that the Taliban imposed in Afghanistan in the late 1990s and that the so-called Islamic State in Iraq and the Levant (ISIL) have practiced beginning in late 2014. In Malaysia, a group called the Sisters in Islam is actively challenging the interpretation of the sharī‘ah practiced there as one that is biased against women and families and not an accurate representation of the Quran and Sunnah. These are some examples of efforts to revisit sharī‘ah to address new situations.
 Intisar Rabb, “Fiqh,” The Oxford Encyclopedia of the Islamic World (Online Resource), 2015, accessed March 18, 2015.