Sunnah is the body of traditions and practices of the Islamic prophet Muhammad that constitute a model for Muslims to follow. For Muslims, the sunnah is what all the Muslims of Muhammad's time supposedly saw, followed, and passed on to the next generations. However, what constitutes the Sunnah, and its interpretation, depends significantly on the specific Islamic sect and school of thought. Sunnis rely on six major canonical hadith collections to document the Sunnah, known as Kutub al-Sittah. For Shias, the sunnah is generally documented in Kutub al-'Arba'a, which give preference to hadiths attributed to the Prophet's family (Ahl al-Bayt) and the Twelve Imams. For Ibadis, the sunnah is documented in the two hadith collections Jami Sahih and Tartib al-Musnad. Sufis hold that Muhammad transmitted his sunnah, including his spiritual values, "through a series of Sufi teachers".
According to classical Islamic theories, the sunnah is embodied in the hadith: verbally transmitted records of the teachings, actions, deeds, and sayings, attributed to Muhammad. Alongside the Qur'an, the Hadith contains the divine revelations (wahy) delivered through Muhammad that make up the primary sources of Islamic law, beliefs, and theology. The sunnah is classified into different types based on Muhammad's specific words (Sunnah Qawliyyah), his actions such as habits and practices (Sunnah Fiiliyyah), and silent approvals (Sunnah Taqririyyah). However, some Muslims, such as Ahl al-Kalam and the Mu'tazilites, have distinguished between the Sunnah and Hadith, accepting the Sunnah as an authoritative practice while being critical of the Hadith's reliability as a source for Islamic law. The Quranist stance on the Sunnah varies from outright rejection to an approach that considers external sources as secondary and dependent on the Qur'an for verification.
