Ibrahim ibn Ma'qil said: I heard Muhammad ibn Isma'il al-Bukhari say: "I was with Ishaq ibn Rahuyah when a man said: 'Why don't you compile an epitome (mukhtasar) of the prophetic ways?' This stayed with me, and was the reason why I compiled this book (the Sahih)." Al-Dhahabi said: "It has been narrated through two firm channels of transmission that al-Bukhari said: 'I extracted this book from about 600,000 (sound) hadiths, and I compiled it over sixteen years, and I made it a plea for what lies between myself and Allah.'" Al-Firabri said: Muhammad ibn Isma'il said to me: "I never included in the Sahih a hadith except I made a major ablution (ghusl) and prayed two rak'at beforehand."
Al-Nawawi said: "The scholars have agreed that the soundest of all hadith compilations are the two Sahihs of al-Bukhari and Muslim, and their vast majority have agreed that the soundest and most beneficial of the two was al-Bukhari's " He continued: "The totality of its hadiths are 7,275 with the repetitions and about 4,000 without."
In his Kitab al-Tatabbu', al-Daraqutni argues for the weakness of 78 hadiths in al-Bukhari, 100 in Muslim, and 32 in both based on isnad and matn criticism.
Al-Nawawi said: "The two Sahihs differ from all other books only in respect to the fact that what is in them is sahih and does not require investigation." Ibn al-Salah said: "Whatever only al-Bukhari or only Muslim narrates enters [also] into the category of what is definitely sahih... except a few letters which some of the expert critics objected to, such as al-Daraqutni and others - and these are known to the specialists." He said this after stating that what they agree upon is "definitely sahih" (maqtu'un bisih.h.atihi) for the Umma. Imam al-Nawawi objected to the terms "definitely sahih" while granting all that is in the Sahihayn the level of "strongly presumed [sahih] until it becomes mutawatir" (yufidu al-zanna ma lam yatawatar) as is the rule with all sahih lone-narrated (ahad) hadiths. But Ibn Kathir differed: "I am with Ibn al-Salah in his conclusion and directives, and Allah knows best." Al-Suyuti in Tadrib al-Rawi cites Ibn Kathir's words verbatim then states: "and this is also my choice and none other." This is because of the standing of the two Sahihs in the Umma and because none of the past Imams in Islam ever declared explicitly and rightly that all they had gathered in their respective books was sahih except al-Bukhari and Muslim, and the verifying experts have confirmed their claim. Al-Suyuti also states:
Shaykh al-Islam said: "What al-Nawawi mentioned in Sharh Sahih Muslim is based on the perspective of the majority (al-aktharin); as for that of the verifying authorities (al-muhaqqiqun), then no. For the verifying authorities also agree with Ibn al-Salah."
By "Shaykh al-Islam" al-Suyuti means the spotless Hafiz and immaculate Imam Ibn Hajar al-'Asqalani and his book al-Nukat 'ala Ibn al-Salah. Al-Suyuti goes on to quote in detail - mostly from Hadi al-Sari - the refutations of Ibn Hajar to al-Daraqutni's criticism, showing that, in effect, the latter fails to invalidate the view of the Sahihayn as 100% sahih.
The fact is that they are all sahih but not all of them reach the same high degree of sahih. This is in essence what al-Dhahabi concluded concerning the few narrators of the Sahihayn whose grading was questioned: "The narration of one such as those, does not go below the rank of hasan which we might call the lowest rank of the sahih." Shaykh Abu Ghudda comments in the margin: "This is an explicit confirmation that al-Bukhari and Muslim did not confine themselves, in the narrations of their respective books, only to narrate hadiths that have the highest degree of sihha." Then again in his appendix (p. 144) he states:
Our Shaykh, the 'Allama Ahmad Shakir - Allah have mercy on him - stated: "The truth without doubt among the verifiers of those who have knowledge of the sciences of hadith... is that the hadiths of the two Sahihs are all sahih and there is not in a single one of them a cause for true [technical] disparagement or weakness. What al-Daraqutni and others criticized is only on the basis that it did not reach the high criterion which each of them defined in their respective books. As for the [criterion of] soundness (sihha) of the hadiths in themselves, then both of them lived up to it.
Dr. Badi' al-Sayyid al-Lahham in his edition of Ibn Kathir's al-Ba'ith al-Hathith (p. 44-45) also closes the discussion on the topic of the Sahihayn with the same words but without attributing them to Shakir. Abu Ghudda concludes (p. 145): "All these texts show that most of what is in Sahih al-Bukhari and Sahih Muslim is of the highest degree of the sahih, and that some of what is in them is not of the highest degree of the sahih." More to the point, our teacher Dr. Nur al-Din 'Itr said in his manual Manhaj al-Naqd fi 'Ulum al-Hadith: "The ruling concerning the hadiths of the two Sahihs is that they are all sahih." All those mentioned above - Ibn al-Salah, al-Nawawi, al-Dhahabi, Ibn Kathir, Ibn Hajar, al-Suyuti, Ahmad Shakir, Abu Ghudda, 'Itr, al-Lahham - agreed on the fact that all of what is in al-Bukhari and Muslim is sahih, and, apart from al-Nawawi's duly recorded dissent, the muhaqqiqun such as Ibn al-Salah, Ibn Kathir, Ibn Hajar, and al-Suyuti consider all the hadiths contained in them maqtu'un bisihhatihi i.e. of the same probative force as mutawatir hadith. Further examination of the positions of the major hadith Masters might add more names to this distinguished list.
The questions are sometimes asked (1) whether all the Ulema of Hadith agree that all the hadiths in al-Bukhari and Muslim are sahih or (2) if there are any scholars who consider them to contain some weak narrations, and (3) whether one who believes that "the Sahihayn are not 100% sahih" is an innovator. As was just shown, some of the greatest hadith authorities such as Ibn al-Salah, Ibn Kathir, and al-Suyuti answered yes to the first question. Imam al-Haramayn (Ibn al-Juwayni) said that if a man swore on pains of divorce that all that is in al-Bukhari and Muslim is sahih his marriage would be safe. But Imam al-Daraqutni said a small number may not reach that level so the answer to the second question has to be yes. Yet the objections were refuted one by one by Ibn Hajar at the beginning of Fath al-Bari and Imam al-Nawawi at the beginning of Sharh Sahih Muslim. The short formula "whether the Sahihayn are or not 100% sahih" remains tenuous and misleading, for the Umma far and wide - meaning the Consensus of the Fuqaha' generation after generation - have been satisfied that they are.
This conclusion excludes the chainless, broken-chained reports, or unattibuted reports sometimes adduced by al-Bukhari in his chapter-titles or appended to certain narrations. An example of the latter is the so-called "suicide hadith" - one of al-Zuhri's unattributive narrations (balaghat) which is actually broken-chained and therefore weak. It does not meet the criteria of hadith authenticity used by the lesser and greater hadith Masters, much less that of al-Bukhari who mentioned it only to show its discrepancy with two other chains whose versions omit the attempted suicide story, and Allah knows best.
The above conclusion is proof that the position that everything that is found in the two Sahihs is rigorously sound refers only to full-chained reports positively attributed to the Prophet ﷺ, and Allah knows best.