The Kutub al-Sittah (Arabic: ٱلْكُتُب ٱلسِّتَّة, romanized: al-Kutub as-Sittah, lit. 'The six books') are six (originally five) books containing collections of hadith (sayings or acts of the Islamic prophetMuhammad) compiled by six Sunni Muslim scholars in the ninth century CE, approximately two centuries after the death of Muhammad. They are sometimes referred to as al-Sahih al-Sittah, which translates as "The Authentic Six". They were first formally grouped and defined by Ibn al-Qaisarani in the 11th century, who add Sunan ibn Majah to the list. Since then, they have enjoyed near-universal acceptance as part of the official canon of Sunni Islam.
Not all Sunni Muslim jurisprudence scholars agree on the addition of Ibn Majah. In particular, the Malikis and Ibn al-Athir consider al-Muwatta' to be the sixth book. The reason for the addition of Ibn Majah's Sunan is that it contains many Hadiths which do not figure in the other five, whereas all the Hadiths in the Muwatta' figure in the other Sahih books.
The first two, commonly referred to as the Two Sahihs as an indication of their authenticity, contain approximately seven thousand hadiths altogether if repetitions are not counted, according to Ibn Hajar.α
According to the Cambridge History of Iran: "After this period commences the age of the authors of the six canonical collections of Sunni hadith, all of whom were Persian, except Imam Malik. The authors of the six collections are as follows:
Muhammad b. Isma'il al-Bukhari, the author of the Sahih Bukhari, which he composed over a period of sixteen years. Traditional sources quote Bukhari as saying that he did not record any hadith before performing ablution and praying. Bukhari died near Samarqand in 256/869–70
Malik was born the son of Anas ibn Malik (notthe Sahabi) and Aaliyah bint Shurayk al-Azdiyya in Medina circa 711. His family was originally from the al-Asbahi tribe of Yemen, but his great grandfather Abu 'Amir relocated the family to Medina after converting to Islam in the second year of the Hijri calendar, or 623 CE. According to Al-Muwatta, he was tall, heavyset, imposing of stature, very fair, with white hair and beard but bald, with a huge beard and blue eyes. In chronological order his work was compiled even earlier than Sahih Bukhari, therefore Al-Muwatta is highly regarded in Islamic literature.
^α Sahih Bukhari and Sahih Muslim contain many of the same Hadith with different chains, and Bukhari in particular also simply repeats the same Hadith with the same chain in multiple chapters. There is disagreement on the amount of unique hadith in the collections due to the disagreements over what Hadith to include as a repeat (chain/text variations) and whether to include same chain repeats in the total number etc.