The book which gave Al-Bukhari his high standing at the zenith of Hadith scholarship in Islamic history is known for short as his Sahih, which means The Authentic. It is universally agreed by Muslim scholars to be the most authentic and accurate work done by a human being. While the Qur’an is God’s word and revelation, which means that no doubt about its authenticity and accuracy may be entertained, Al-Bukhari’s Sahih comes second to it in this respect. The full name of the book is Al-Jami’ Al-Sahih Al-Musnad Al-Mukhtasar min Hadith Rasool Allah (Salla Allah alaihi wa sallam) wa Sunanihi wa Ayyamih.
Each word in the name of the book is carefully chosen and clearly significant. Thus, it is Al-Jami’ which means that it is ‘all-embracing’ in the sense that it leaves out no area of Hadith. It deals with all aspects on which the Prophet spoke, including the principles of faith, social standards, morality, war, etc. It is Sahih which means that it includes only what is authentic. No Hadith that is lacking in authenticity is entered. It is Musnad, which means that every Hadith is stated with its chain of transmission clearly given, so that verification of each Hadith is shown to have been done according to the highest standards. It is also Mukhtasar which means that it is concise, not giving all Hadiths that could have been included under any chapter. Min Hadith Rasool Allah (Salla Allah alaihi wa sallam) spells the subject matter of the book, which is the verbal statements made by the Prophet (peace be upon him). Wa Sunanihi wa Ayyamih makes it clear that the book is not limited to the Prophet’s verbal statements, but also outlines his practices (i.e. sunan) and the main events of his lifetime (i.e. ayyam).
Thus we see that Al-Bukhari intended his book to be encyclopaedic in scope, yet concise in material, so that it would not be too long or too voluminous for people to study. In order to meet these requirements, Al-Bukhari took a great deal of care in his selection. He was at the prime of his scholarship when he embarked on his momentous task, which he started in Makkah, living close to the Kaaba. It took him no less than 16 years to finalize this book. Al-Bukhari mentions that when he made up his mind to include a certain Hadith, he would first offer the prayer known as istikharah, which is a special prayer seeking God’s help in determining one’s course of action. This means that after having done all that he could to be absolutely certain that a Hadith meets his stringent criteria of authenticity, having studied every aspect that might have a bearing on that, he would leave the final verdict to God, through his prayer of istikharah.
We may wonder why would it take Al-Bukhari all this time to make his selection, when he was a scholar of the highest caliber, and he could rely on his exceptional memory. We should remember that Al-Bukhari had memorized no less than 600,000 Hadiths, but he included in his Sahih only 9,082, many of which are repeated more than once. Selecting such a small number from such a great wealth is by no means an easy task, and requires a great deal of diligence. So, what was Al-Bukhari’s criterion for selection?
It is well known that a Hadith could be rejected if it is flawed in its text or chain of transmission. There are well known reasons why a Hadith may be flawed in its text, such as its being in conflict with a clear Qur’anic text. But the most important and much harder task is to establish its authenticity with regard to its chain of transmission. For this reason, every reporter mentioned in any chain is studied and graded. The grading would be first of all on the basis of the person’s character. He should be a person of the highest integrity, truthful in everything he or she says. If it is known that a person had said a lie, even in ordinary speech, then that person is downgraded and classified as unacceptable. He should also be reliable in his reporting, knowing fully well from whom he heard each Hadith he reports. To clarify, everyone may study under several teachers. When he reports a Hadith, he must attribute it to the teacher from whom he had heard it. If he is confused with regard to his teachers, attributing one Hadith to one teacher when he had heard it from another, he is downgraded, and Al-Bukhari would not accept his Hadiths.
Moreover, scholars of Hadith make it a condition that when one scholar reports a Hadith from another, the two should be contemporaries, even though for a short while. Thus, if it is known that a scholar was only 10 when an earlier scholar died, and the younger declares that he reports his Hadith from the former, this is unacceptable. But Al-Bukhari goes further than this and requires that the two must have physically met, at least once. This is determined by the later scholar declaring very clearly that he personally heard a Hadith from the earlier one. If this is left implicit, it is unacceptable to Al-Bukhari.
Moreover, when reporting from a famous scholar of Hadith, who had many students who became scholars in their own right, Al-Bukhari classifies them into groups, putting those who were known to have been close to their teacher for a long period in the top group. He normally relies on those in the top group.
To give an example of what these conditions meant we may quote Al-Bukhari’s statement regarding Ibn Abu Laila, a leading scholar of Fiqh and a judge who was a contemporary of Abu Haneefah. Al-Bukhari says: "Ibn Abu Laila was a truthful man, but I do not narrate his Hadiths, because he did not know which of them were authentic and which were not. Whoever was of the same type I would not include his Hadiths." Thus, the man is rejected despite being trustworthy and of high standing as a scholar. His rejection is due to the fact that he did not pay much attention to Hadith. Rather, his scholarship was in different disciplines. In fact, Al-Bukhari’s view of Ibn Abu Laila is shared by Ahmad ibn Hanbal.
Moreover, Al-Bukhari took exceptional care to include short and long chains of transmission, in order to indicate the width of his scholarship. Thus, although he started his Hadith learning almost 200 years after the Prophet’s death, a number of his Hadiths have a chain of transmission which includes only three reporters. This means that he heard the Hadith in question from a scholar who heard it from one that met at least one of the Prophet’s companions and heard it from him, while the Prophet’s companion heard it directly from the Prophet. This level of reporting is called high isnad, which is a mark of distinction. But Al-Bukhari also includes different levels of reporting, in which some Hadiths would have a chain of transmission in not less than eight reporters. In between there are all types of variety. These differences make for a high degree of scholarship, as it establishes all authentic and different routes of transmission of the Prophet’s Hadiths, indicating which scholars heard from which and how reliable is each. We also note that Al-Bukhari includes Hadiths reported by some of his close contemporaries, even those who were younger than him. Again this shows that he was well aware of the grades of his contemporaries and who of them were highly reliable.
But we also note that he includes in his Sahih only a few Hadiths of those related by the top scholars of Hadith. Thus, we see in his Sahih only two Hadiths related by Ahmad ibn Hanbal, his teacher with whom he was very close. This was the practice of many Hadith scholars. Thus, Ahmad includes in his book Al-Musnad only four Hadiths transmitted by Al-Shafie from Malik from Nafi’, which is one of the most authentic chains of transmission, despite the fact that Ahmad was a student of Al-Shafie and the latter a student of Malik. This is due to the fact that these scholars had their own books of Hadiths which were well documented. Malik, for example, wrote Al-Muwatta’, which is rated on a par with Al-Bukhari’s and Muslim’s Sahih. They felt that the Hadiths related in these books were safe and guaranteed not to be lost. They concentrated on other Hadiths to ensure their preservation.