The Qur'an is the central religious text of Islam, which Muslims consider the verbatim word of God and the final divine revelation. It is regarded widely as the finest piece of literature in the Arabic language. Muslims believe that the Qur'an was verbally revealed through the angel Jibr?l (Gabriel) from God to Muhammad over a period of approximately twenty-three years beginning in 610 AD. Furthermore, Muslims believe that the Quran was precisely memorized, recited and exactly written down by Muhammad's companions, the Sahaba.
A body of commentary and explication (tafs?r), aimed at explaining the meanings of the Quranic verses.
Asb?b al-nuz?l is a secondary genre of Qur'anic exegesis (tafsir) directed at establishing the context in which specific verses of the Qur'an were revealed.
Sunna denotes the practice of Islamic prophet Muhammad that he taught and practically instituted as a teacher of the shar?'ah and the best exemplar. The sources of sunna are usually oral traditions found in collections of Hadith and S?ra (prophetic biography). Unlike the Qur'an, Muslims do not agree on the same set of texts or sources of Sunnah, and they emphasize different collections of hadith based on to which Islamic school or branch they belong.