Principles of Islamic jurisprudence in the context of "Islamic law"

Sunni Islam is the largest branch of Islam and the largest religious denomination in the world. It holds that Muhammad did not appoint any successor and that his closest companion Abu Bakr (r. 632–634) rightfully succeeded him as the caliph of the Muslim community, being appointed at the meeting of Saqifa. This contrasts with the Shia view, which holds that Muhammad appointed Ali ibn Abi Talib (r. 656–661) as his successor. Nevertheless, Sunnis revere Ali, along with Abu Bakr, Umar (r. 634–644) and Uthman (r. 644–656) as 'rightly-guided caliphs'.

The term Sunni means those who observe the sunna, the practices of Muhammad. The Quran, together with hadith (especially the Six Books) and ijma (scholarly consensus), form the basis of all traditional jurisprudence within Sunni Islam. Sharia legal rulings are derived from these basic sources, in conjunction with consideration of public welfare and juristic discretion, using the principles of jurisprudence developed by the four legal schools: Hanafi, Hanbali, Maliki and Shafi'i.

Sharia (/ʃəˈriːə/; Arabic: شَرِيعَة, romanized: sharīʿah, lit. 'path [to water]', IPA: [ʃaˈriːʕa]), also transliterated as Sharī'ah, Shari'a, or Shariah, is a body of religious law that form the Islamic tradition based on scriptures of Islam, particularly the Qur'an and hadith. In Islamic terminology sharīʿah refers to immutable, intangible divine law, in contrast to fiqh (Islamic jurisprudence), which refers to its interpretations by Islamic scholars. Sharia, or fiqh as traditionally known, has always been used alongside customary law from the very beginning in Islamic history; it has been elaborated and developed over the centuries by legal opinions issued by qualified jurists – reflecting the tendencies of different schools – and integrated with various economic, penal and administrative laws issued by Muslim rulers; and implemented for centuries by judges in the courts until recent times, when secularism was widely adopted in Islamic societies.

Traditional theory of Islamic jurisprudence recognizes four sources for al-sharia: the Qur'an, sunnah (or authentic ahadith), ijma (lit. consensus) (may be understood as ijma al-ummah (Arabic: إجماع الأمة) – a whole Islamic community consensus, or ijma al-aimmah (Arabic: إجماع الائـمـة) – a consensus by religious authorities), and analogical reasoning. It distinguishes two principal branches of law, rituals (Ibadah) and social dealings (Muamalat); subsections family law, relationships (commercial, political / administrative) and criminal law, in a wide range of topics assigning actions – capable of settling into different categories according to different understandings – to categories (ahkam) mainly as: mandatory, recommended, neutral, abhorred, and prohibited. Beyond legal norms, Sharia also enters many areas that are considered private practises today, such as belief, worshipping, ethics, clothing and lifestyle, and gives to those in command duties to intervene and regulate them.

Ijtihad (/ˌɪdʒtəˈhɑːd/ IJ-tə-HAHD; Arabic: اجتهاد ijtihād [ʔidʒ.tihaːd], lit. 'physical effort' or 'mental effort') is an Islamic legal term referring to independent reasoning by an expert in Islamic law, or the thorough exertion of a jurist's mental faculty in finding a solution to a legal question. It is contrasted with taqlid (imitation, conformity to legal precedent). According to classical Sunni theory, ijtihad requires expertise in the Arabic language, theology, revealed texts, and principles of jurisprudence (usul al-fiqh), and is not employed where authentic and authoritative texts (Qur'an and hadith) are considered unambiguous with regard to the question, or where there is an existing scholarly consensus (ijma). Ijtihad is considered to be a religious duty for those qualified to perform it. An Islamic scholar who is qualified to perform ijtihad is called a "mujtahid".

For the first five centuries of Islam, the practice of ijtihad continued in theory and practice among Sunni Muslims. It then first became subject to dispute in the 12th century. By the 14th century, development of classic Islamic jurisprudence or fiqh prompted leading Sunni jurists to state that the main legal questions in Islam had been addressed, and to call for the scope of ijtihad to be restricted. In the modern era, this gave rise to a perception amongst Orientalist scholars and sections of the Muslim public that the so-called "gate of ijtihad" was closed at the start of the classical era. While recent scholarship established that the practice of Ijtihad had never ceased in Islamic history, the extent and mechanisms of legal change in the post-formative period remain a subject of debate. Differences amongst the Fuqaha (jurists) prevented Sunni Muslims from reaching any consensus (Ijma) on the issues of continuity of Ijtihad and existence of Mujtahids. Thus, Ijtihad remained a key aspect of Islamic jurisprudence throughout the centuries. Ijtihad was practiced throughout the Early modern period and claims for ijtihad and its superiority over taqlid were voiced unremittingly.

Maslaha or maslahah or maslahat (Arabic: مصلحة, lit. 'benefit, public interest') or maslaha mursala (Arabic: مصالح مرسلة, lit. '"sent", "transmitted", "unbonded", "open" or "unconditional" public interest'), comes from the term "Salihat" (good deeds, also linked to Islah and Istislah), is a concept in Sharia (Islamic divine law) regarded as a basis of law. It forms a part of extended methodological principles of Islamic jurisprudence (uṣūl al-fiqh) and denotes prohibition or permission of something, according to necessity and particular circumstances, on the basis of whether it serves the public interest of the Muslim community (ummah). In principle, maslaha is invoked particularly for issues that are not regulated by the Qur'an, the sunnah (the teachings and practices of the Islamic prophet Muhammad), or qiyas (analogy). The concept is acknowledged and employed to varying degrees depending on the jurists and schools of Islamic jurisprudence (madhhab). The application of the concept has become more important in modern times because of its increasing relevance to contemporary legal issues. The opposite term of maslaha is mafsada (مفسدة, harm). Islamic politics is itself predicated on maslaha, and is such changeable, as it must respond to the exigencies of time. The term is different from bidah.

A mufti (/ˈmʌfti/; Arabic: مفتي [muftiː], listen) is an Islamic jurist qualified to issue a nonbinding opinion (fatwa) on a point of Islamic law (sharia). The act of issuing fatwas is called iftāʾ. Muftis and their fatāwa have played an important role throughout Islamic history, taking on new roles in the modern era.

Tracing its origins to the Quran and early Islamic communities, the practice of ifta crystallized with the emergence of the traditional legal theory and schools of Islamic jurisprudence (madhahib). In the classical legal system, fatwas issued by muftis in response to private queries served to inform Muslim populations about Islam, advise courts on difficult points of Islamic law, and elaborate substantive law. In later times, muftis also issued public and political fatwas that took a stand on doctrinal controversies, legitimized government policies or articulated grievances of the population.

Al-Ghazali (c. 1058 – 19 December 1111), archaically Latinized as Algazelus, was a Shafi'i Sunni Muslim scholar and polymath. He is known as one of the most prominent and influential jurisconsults, legal theoreticians, muftis, philosophers, theologians, logicians and mystics in Islamic history.

He is considered to be the 11th century's mujaddid, a renewer of the faith, who, according to the prophetic hadith, appears once every 100 years to restore the faith of the Islamic community. Al-Ghazali's works were so highly acclaimed by his contemporaries that he was awarded the honorific title "Proof of Islam" (Ḥujjat al-Islām). Al-Ghazali was a prominent mujtahid in the Shafi'i school of law.