Hadith literature consists of mostly raw information and a religious scholar, like a good judge, must sift through this enormous data to determine what’s applicable and more trustworthy. Truth is all that matters. If history or other Hadiths do end up proving a Hadith wrong, a Muslim should have no hesitancy in rejecting a Hadith After all, a Hadith is simply somebody’s report, passed down from generation to generation, subject to human error. The Hadith compilers did their best to pick the most authentic Hadiths, but that doesn’t mean that they were always successful. Of the 600,000 or so Hadiths that were current in his time, Bukhari chose only about 7,000. But as for those who do not know much about Islam—and that unfortunately includes many Muslims— they will keep insisting that every Muslim must accept every single Hadith. That is simply false.
Based on the information that we have available, Muslim scholars have classified various Hadiths. A Hadith can be ‘sahih'(sound/authentic), ‘hasan sahih’ (higher level than sahih but lower than sahih),’hasan'(approved), ‘hasan sahih gharib’ (hasan in regard to soundness but gharib in regard to chain of transmitters), ‘gharib’ (uncommon, number of narrators is reduced to one at any stage), ‘mutawatir’ (continuous), ‘mashhur’ (well known), ‘da’if'(weak), ‘mawdu’ (forged), ‘marsal’ (forwarded), ‘marfu’ (traced directly), ‘mudallas’ (deceptive), ‘shadh’ (isolated), ‘munkar’ (disapproved), ‘munqati’ (disjoined), ‘muttasil’ (joined), ‘maqtu’ (broken), ‘mawquf’ (suspended), ‘matruk’ (abandoned), ‘mu’aalaq’ (one or more consecutive transmitters are omitted), ‘mahfudh’ (contradictory), ‘hadith qudsi’ (holy narration). [The last classification, Hadith Qudsi, refers to Hadiths in which the Prophet was quoted as saying something that God had told him].
In addition, the Who’s Who of narrators has been developed to verify their reliability, and that too needs to be taken into account. It is not as easy as looking up a Hadith and issuing a ruling.
No Muslim scholar has ever said that the task of evaluating Hadiths has come to an end. But despite their obvious flaws, Hadith literature is helpful in many ways. It provides some necessary details that would indeed be difficult to find anywhere else. Some Hadiths have been repeated so many times and have come to us from so many different sources that it would be foolish to deny them. And, ironically, it’s contradictions within Hadith literature itself that allows one to dig deeper (consult other sources), and that sometimes sets the record straight.
Besides Quran and Hadith, there are two other sources of Islam: The Sunnah (the practice) of the Prophet has been transmitted from generation to generation, which includes the method of praying, fasting, Hajj etc. The second is history, and actually some history books such as Ibn Ishaq’s “Sira” predates most Hadith books.