(العرف) is an Arabic Islamic term referring to the custom, or 'knowledge', of a given society. To be recognized in an Islamic society, must be compatible with the Sharia law. When applied, it can lead to the deprecation or inoperability of a certain aspect of fiqh (Islamic jurisprudence). is a source of Islamic legal rulings where there are not explicit primary texts of the Qur'an and Sunnah specifying the ruling. can also specify something generally established in the primary texts. Terminology The term , meaning "to know", refers to the customs and practices of a given society. History was first recognized by Abū Yūsuf (d. 182/798), an early leader of the Ḥanafī school, though it was considered part of the , and not as formal source. Later al-Sarak̲h̲sī (d. 483/1090) opposed it, holding that custom cannot prevail over a written text. Scriptural basis The "maxim" that custom is an authoritative source for Islamic law "appears in the Quran and Hadith". One hadith narrated by Ibn Mas'ud stated 'Whatever the Muslim saw as good is [considered] good by God, and whatever the Muslim saw as evil is evil according to God.'" Although this was not formally included in Islamic law, the Sharia recognizes customs that prevailed at the time of Muhammad but were not abrogated by the Qur'an or the Sunnah (called "Divine silence"). Practices later innovated are also justified, since Islamic tradition says what the people, in general, consider good is also considered as such by Allah (see God in Islam). According to some sources, holds as much authority as (consensus), and more than (legal reasoning by analogy). is the Islamic equivalent of "common law". In the application of , custom that is accepted into law should be commonly prevalent in the region, not merely in an isolated locality. If it is in absolute opposition to Islamic texts, custom is disregarded. However, if it is in opposition to , custom is given preference. Jurists also tend to, with caution, give precedence to custom over doctoral opinions of highly esteemed scholars.