In Islam, sunnah, also spelled sunna, are the traditions and practices of the Islamic prophet Muhammad that constitute a model for Muslims to follow. The sunnah is what all the Muslims of Muhammad's time evidently saw and followed and passed on to the next generations. According to classical Islamic theories, the sunnah are documented by hadith, and alongside the Quran are the divine revelation (wahy) delivered through Muhammad that make up the primary sources of Islamic law and belief/theology. Differing from Sunni classical Islamic theories are those of Shia Muslims, who hold that Imams interpret the sunnah, and Sufi who hold that Muhammad transmitted the values of sunnah "through a series of Sufi teachers".

Hadith or Athar refers to what most Muslims and the mainstream schools of Islamic thought believe to be a record of the words, actions, and the silent approval of the Islamic prophet Muhammad as transmitted through chains of narrators. In other words, the ḥadīth are attributed reports about what Muhammad said and did.