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,
Hadith terminology its source. This provides confirmation that the "hadith" is authentically attributed to its source at a level above reasonable doubt. This is due to its being beyond historical possibility that narrators could have conspired to forge a narration. In contrast, an "ahaad hadith" is a narration the chain of which has not reached a number sufficient to qualify as "mutawatir". "Hadiths" can be "mutawatir" in both actual text and meaning: The second category, "ahaad" ( meaning "singular") narration, refers to any "hadith" not classified as "mutawatir". Linguistically, "hadith ahad" refers to a "hadith" narrated by only one narrator. In "hadith"