The Kitāb al-Umm is a book of law

Law

Law is a system of rules and guidelines which are enforced through social institutions to govern behavior, wherever possible. It shapes politics, economics and society in numerous ways and serves as a social mediator of relations between people. Contract law regulates everything from buying a bus...

 that is used as an authoritative guide by the Shafi'i

Shafi'i

The Shafi'i madhhab is one of the schools of fiqh, or religious law, within the Sunni branch of Islam. The Shafi'i school of fiqh is named after Imām ash-Shafi'i.-Principles:...

 school of fiqh

Fiqh

Fiqh is Islamic jurisprudence. Fiqh is an expansion of the code of conduct expounded in the Quran, often supplemented by tradition and implemented by the rulings and interpretations of Islamic jurists....

 (Islamic jurisprudence) within the Sunni

Sunni Islam

Sunni Islam is the largest branch of Islam. Sunni Muslims are referred to in Arabic as ʾAhl ūs-Sunnah wa āl-Ǧamāʿah or ʾAhl ūs-Sunnah for short; in English, they are known as Sunni Muslims, Sunnis or Sunnites....

 branch of Islam

Islam

Islam . The most common are and .   : Arabic pronunciation varies regionally. The first vowel ranges from ~~. The second vowel ranges from ~~~...

. The work was composed by the founder of the Shafi'i school, Imām ash-Shāfi‘ī

Muhammad ibn Idris ash-Shafi`i

Abū ʿAbdullāh Muhammad ibn Idrīs al-Shafiʿī was a Muslim jurist, who lived from 767 CE to 820 CE. He was active in juridical matters and his teaching eventually led to the Shafi'i school of fiqh named after him. Hence he is often called Imam al-Shafi'i...

 (767-820 CE). The term "al-Umm" means "the exemplar." The Kitab al-Umm is noted for its hermeneutic approach to developing legal principles, basing them on revelation rather than traditional authority.