Hadith remembers God unceasingly. (Al-Ahzab 33: 21) The hadith literature is based on spoken reports in circulation after the death of Muhammad. Unlike the Qur'an, ahadith were not promptly written down during Muhammad's life or immediately after his death. Hadith were evaluated and gathered into large collections during the 8th and 9th centuries, generations after the death of Muhammad, after the end of the era of the "rightful" Rashidun Caliphate, over from where Muhammad lived. "Many thousands of times" more numerous than Quranic verse, ahadith have been described as resembling layers surrounding the “core” of the Islamic belief (the Quran). Well-known,
Criticism of Hadith "in the early Islamic centuries there could be no better way of promoting a cause, an opinion, or a faction than to cite an appropriate action or utterance of the Prophet." This gave strong incentive to fabricate hadith. According to Daniel Brown, the major causes of corruption of Hadith literature are: Other criticism made of ahadith include Orthodox Muslims do not deny the existence of false "hadith", but believe that through the work of hadith scholars, these false "hadith" have been largely eliminated. al-Shafi'i himself, the founder of the proposition that “sunna” should be made up exclusively of specific precedents