Also, Mirch, Do you know how the hadithes were compiled? This article tells you.
*Collection of Hadithes *
The term Sunnah refers to whatever has been recorded of the Prophet's statements, practices, actions, and approvals. As the Qur'an was revealed in parts and passages, over a period of 23 years, it was written down, as dictated by the Prophet (peace be upon him) who received it directly from the angel Gabriel. At first, the Prophet did not wish that his own statements be recorded. This was a precaution aiming to prevent any mix up of the Hadith with the Qur'an. This was the right policy, particularly when we consider the scarcity of writing materials at the time and the fact that the Arabs were largely an illiterate community. Few of them could read and write. However, he allowed certain people to write what they heard from him, realizing that they were unlikely to confuse his statements with the Qur'an. One of these who had their own Hadith collections was Abdullah ibn Amr ibn Al-Aas.
When the Qur'an was collated and reference copies were sent to the main population centers of the Muslim state, more of the Prophet's companions and the following generation had their Hadith collections. These were either the ones they heard directly from the Prophet, or ones they learned from his companions. In the latter case, they would mention the reporter. However, the Prophet's companions were very keen to quote the Prophet's words most accurately, because they heard his warning: "Whoever deliberately attributes to me what I have not said shall have his place in hell." Fearing the strong warning, the Prophet's companions would not attribute a statement to the Prophet unless they were absolutely certain of its exact wording. Otherwise, they would declare that they were reporting the meaning, or they would put it in their own words, such as saying: "The Prophet did not allow this", or "the Prophet approved that."
When political divisions occurred in the Muslim state, and alien groups tried to exploit such divisions, they realized the strong hold Islam had on its followers. Hence, they tried to give their political stand a religious cover. They knew that only in this way could they hope to make the division permanent. They could not provide such a cover on the basis of the Qur'an, because the Qur'an is a very accurate text, known by so many people, with clear meanings, and nothing could be introduced into it. Hence they could only resort to attributing false statements to the Prophet and claim that these were Hadiths.
Hence, scholars insisted that a Hadith should not be quoted unless its reporters were known. It was then that a "sanad', or chain of transmitters, was required for every Hadith. We should remember that this happened very early in Islamic history. The Caliph Uthman was killed in year 36 H, and Ali was assassinated in year 40, i.e. 26 and 30 years, respectively, after the Prophet had passed away. Fabrication began around this time and acquired more momentum later. Hence, scholars started to be more careful in accepting what is attributed to the Prophet.
Collecting the Hadiths in book form was started by the Caliph Umar ibn Abd Al-Azeez, who assumed the Caliphate in year 99 and died in 101. He wrote to provincial governors, particularly the governor of Madinah, to ensure that all authentic Hadiths are collected. As a result, Muhammad ibn Shihab Al-Zuhri produced the first Hadith anthology. Al-Zuhri, who died in 124, was a scholar of the highest calibre. Among his students were Imam Malik, Al-Layth ibn Saad the leading Egyptian scholar and Al-Awzaie, the great scholar of Syria. He had dedicated his life to Islamic scholarship, and to the study of Hadith. Hence, he was the most suited for the task. He thus led the way. Imam Malik (died 179) then produced Al-Muwatta', an anthology of authentic Hadiths classified according to subject matter.
Hadith scholarship continued to flourish. By then, each sanad or chain of transmission was carefully examined. The idea of classifying reporters of Hadith into "acceptable" or "unacceptable" has developed and standards were clearly formulated. This is an area of study unknown in any other community or civilization. It became a "science' known as "Al-Jarh Wal-Taadeel", with very strict rules. Hadith scholars were most diligent in refining and maintaining the highest standards. They were everywhere in the Muslim world, taking care of this highly distinguished branch of scholarship. This science of distinguishing reliable reporters achieved its perfection by the two scholars Yahya ibn Maeen (died 234) and Ahmad ibn Hanbal (died 241). Ahmad was one of Al-Bukhari's teachers. Indeed, Al-Bukhari studied under both, as well as many other scholars.
By this time, many scholars had their own books of Hadith in which they entered what they deemed as authentic. It was about this time that one of the top scholars of Hadith, Ishaq ibn Rahaweih (died 238) suggested to his students that they should produce "a short collection of only authentic Hadiths" to make it available to people. The suggestion was taken up by one of those students, Muhammad ibn Ismaeel Al-Bukhari, (died 256) and the result was his Saheeh anthology. It took him 16 years of diligent work to produce it, classifying it according to subject, and entering only a very small number of Hadiths under every subheading. The selection was made according to a very stringent set of rules. For example, it was not enough that a reporter should have been alive at the same time as the one he is quoting; their meeting should be confirmed beyond doubt. When Al-Bukhari finished his work,** he gave it to Imam Ahmad ibn Hanbal for review. Ahmad, the founder of the Hanbali school of thought, approved it.
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The other five collections were produced shortly afterward. They differ in the rules they applied, but their standards were very high.
How come that Hadiths graded as "poor in authenticity" found their way into such anthologies. To start with, this does not apply to Al-Bukhari and Muslim. We can almost say the same about Malik's and Al-Nassaie's anthologies. The reason lies mainly in the judgment of a particular reporter. One scholar might consider him "unreliable" while another classifies him as "reliable." Since Hadith scholars did not wish to provide a very detailed account of the reasons for unacceptability, because Islam disapproves of publicizing people's faults, information about some reporters might be lacking. Scholars would rule that a certain reporter is "suspect" or "scholars set him aside" or "unreliable." Only when they had to warn against someone that they would say things like "liar", "fabricator", "had un-Islamic beliefs."
Hadith scholarship continued after these great scholars. The result is that we have numerous anthologies, and encyclopedic biographical studies of Hadith reporters, to ensure that we can distinguish what is authentic of Hadiths attributed to the Prophet and what is unauthentic .