Sunnah is a saying attributed to the Islamic prophet Muhammad (a hadith), namely I have left among you two matters by holding fast to which, you shall never be misguided: the Book of God and my Sunna. It is an often quoted saying regarding the sources of Islam. The authenticity of this hadith is rejected by many Shi’a. The concept itself is not rejected, as most Muslims hold that Islam is derived from two sources: one being infallible and containing compressed information — the Qur’an —and another being a detailed explanation of the everyday application of the principles established in the Qur’an: The Sunnah, or the living example of Muhammad.
Hadith literature refers to the oral tradition about the words and deeds (Sunnah) of Muhammad. The statement that Islam has these two sources has been attributed to Muhammad. The Sunni Muslims accept this attribution as sahih (authentic) and hence a hadith; whereas the Shi’a Muslims reject this as being mawdoo (fabricated), and not a separate hadith, arguing that nowhere is it recorded in the Six Authentic Books of the Sunni’s (Sahih Sitta). The hadith in the Six Authentic Books are generally accept as authentic throughout Islam.
The Qur’an and Sunnah hadith is reported in other books as having been said during Muhammad’s Farewell Sermon atop Mount Arafat after his Last Pilgrimage.(e.g. Malik Muwatta)
Slightly varied versions are cited in many Sunni hadith works. Among those are:
al-Jami’ li-Akhlaq al-Rawi by Al-Khatib
Sira al-Nabawiyyah by Ibn Hisham
John Esposito explains the importance of the Hadith in Islam: “the Prophet Muhammad is seen as the living Quran, the embodiment of God’s will in his behavior and words. Sunni Muslims … take their name from the sunnah, meaning those who follow the example of the Prophet”. Prof. Fatih Okumus refers to Muhammad as “the walking Qur’an,” with the Sunnah giving an example to follow.