Kutub al-Sittah in the context of "Sunnah"

Sahih al-Bukhari (Arabic: صحيح البخاري, romanized: Ṣaḥīḥ al-Bukhārī) is the first hadith collection of the Six Books of Sunni Islam. Compiled by Islamic scholar al-Bukhari (d. 870) in the musannaf format, the work is valued by Sunni Muslims, alongside Sahih Muslim, as the most authentic after the Qur'an.

Al-Bukhari organized the book mostly in the Hijaz at the Sacred Mosque of Mecca and the Prophet's Mosque of Medina and completed the work in Bukhara around 846 (232 AH). The work was examined by his teachers Ahmad ibn Hanbal, Ali ibn al-Madini, Yahya ibn Ma'in and others.

Sahih Hadith (Arabic: الحديث الصحيح, al-Hadith al-Ṣaḥīḥ) in Hadith terminology, may be translated as "authentic hadith (prophetic narration)" or "sound hadith (prophetic narration)". Ibn Hajar defines a hadith that is ṣaḥīḥ lidhātihi ("ṣaḥīḥ in and of itself") as a singular narration (ahaad; see below) conveyed by a trustworthy, completely competent person, either in his ability to memorize or to preserve what he wrote, with a muttaṣil ("connected") isnād ("chain of narration") that contains neither a serious concealed flaw (ʻillah, Arabic:علة) nor irregularity (shādhdh). He then defines a hadith that is ṣaḥīḥ lighairihi ("ṣaḥīḥ due to external factors") as a hadith "with something, such as numerous chains of narration, strengthening it." In the Sunni branch of Islam, the canonical hadith collections are the six books (Kutub al-Sittah) listed below.

The Mahdi (Arabic: ٱلْمَهْدِيّ, romanized: al-Mahdī, lit. 'the Guided'), also Masih al-Mahdi (Arabic: المسيح المهدي, romanized: al-Masīḥ al-Mahdī, lit. 'the Guided Redeemer'), is a messianic figure in Islamic belief. He is comparable to the Christian idea of the return of Jesus and the Mashiach ben David in Judaism. He is believed to appear at the End of Times to rid the world of evil and injustice. He is said to be a descendant of Muhammad and will appear shortly before Jesus.

The Mahdi is mentioned in several compilations of hadith, but absent from the Quran and the two most-revered Sunni hadith collections (Sahih al-Bukhari and Sahih Muslim). As such, he plays only a marginal role in Sunni Islam and some Sunni theologians have rejected the concept of the Mahdi altogether. However, the Mahdi plays a significant role among Twelver Shias, who believe that the Mahdi is Imam Muhammad al-Mahdi, the twelfth Imam, son of the eleventh Imam Hasan al-Askari (d. 874), who is said to be in occultation (ghayba) by divine will.

Sahih Muslim (Arabic: صحيح مسلم, romanized: Ṣaḥīḥ Muslim) is the second hadith collection of the Six Books of Sunni Islam. Compiled by Islamic scholar Muslim ibn al-Ḥajjāj (d. 875) in the musannaf format, the work is valued by Sunnis, alongside Sahih al-Bukhari, as the most important source for Islamic religion after the Qur'an.

Sahih Muslim contains approximately 5,500 - 7,500 hadith narrations in its introduction and 56 books. Kâtip Çelebi (died 1657) and Siddiq Hasan Khan (died 1890) both counted 7,275 narrations. Muhammad Fuad Abdul Baqi wrote that there are 3,033 narrations without considering repetitions. Mashhur ibn Hasan Al Salman, a student of Albanian Islamic scholar Al-Albani (died 1999), counted 7,385 total narrations, which, combined with the ten in the introduction, add up to a total of 7,395. Muslim wrote an introduction to his collection of hadith, wherein he clarified the reasoning behind choosing the hadith he chose to include in his Sahih.

Abū al-Ḥusayn Muslim ibn al-Ḥajjāj ibn Muslim ibn Ward al-Qushayrī an-Naysābūrī (Arabic: أبو الحسين مسلم بن الحجاج بن مسلم بن وَرْد القشيري النيسابوري; after 815 – May 875 CE / 206 – 261 AH), commonly known as Imam Muslim, was an Islamic scholar from the city of Nishapur, particularly known as a muhaddith (scholar of hadith). His hadith collection, known as Sahih Muslim, is one of the six major hadith collections in Sunni Islam and is regarded as one of the two most authentic (sahih) collections, alongside Sahih al-Bukhari.

Sunan Abi Dawud (Arabic: سنن أبي داود, romanized: Sunan Abī Dāwūd) is the third hadith collection of the Six Books of Sunni Islam. It was compiled by scholar Abu Dawud al-Sijistani (d. 889).

Sunan al-Sughra (Arabic: سنن الصغرى, romanized: Sunan al-Ṣughrā), also known as Sunan al-Nasa'i (Arabic: سنن النسائي, romanized: Sunan al-Nasāʾī), is one of the Kutub al-Sittah (six major hadith collections), and was collected by al-Nasa'i (214 – 303 AH; c. 829 – 915 CE).

Sunan Ibn Mājah (Arabic: سُنَن ٱبْن مَاجَه) is one of the six major Sunni hadith collections (Kutub al-Sittah). The Sunan was authored by Ibn Mājah (born 824 CE, died 887CE).