Sunnah (sunnah, سنة, Arabic: [sunna], plural سنن sunan [sunan]) is the verbally transmitted record of the teachings, deeds and sayings, silent permissions (or disapprovals) of the Islamic prophet Muhammad, as well as various reports about Muhammad's companions. The Quran (the holy book of Islam) and the Sunnah make up the two primary sources of Islamic theology and law. The Sunnah is also defined as "a path, a way, a manner of life"; "all the traditions and practices" of the Islamic prophet that "have become models to be followed" by Muslims.
In the pre-Islamic period, the word sunnah was used with the meaning "manner of acting", whether good or bad. During the early Islamic period, the term came to refer to any good precedent set by people of the past, including the Islamic prophet Muhammad. Under the influence of Al-Shafi'i, who argued for priority of Muhammad's example as recorded in hadith over precedents set by other authorities, the term al-sunnah eventually came to be viewed as synonymous with the sunnah of Muhammad.
The sunnah of Muhammad includes his specific words (Sunnah Qawliyyah), habits, practices (Sunnah Fiiliyyah), and silent approvals (Sunnah Taqririyyah). According to Muslim belief, Muhammad was the best exemplar for Muslims, and his practices are to be adhered to in fulfilling the divine injunctions, carrying out religious rites, and moulding life in accord with the will of God. Instituting these practices was, as the Quran states, a part of Muhammad's responsibility as a messenger of God. Recording the sunnah was an Arabian tradition and, once people converted to Islam, they brought this custom to their religion.