How many works of Hadith in total exist? If someone wants to develop an opinion about a certain area of life based on hadith how can he/she be sure that he/she has honestly considered all the points of view which are ascribed to Prophet (sws). I mean there are many matters in which the ahadith conflict. How can someone make sure that he or she has seen all possible available ahadith on a certain topic?
Thank you for writing to us. When a Muslim scholar intends to study the religious point of view on an issue he looks into the Qur'an for guidance first of all. Then there is the Sunnah of the Prophet (sws). By Sunnah I mean the practices the Prophet (sws) instituted as part of the religion and taught to the entire generation of his addressees who then passed it on to the next generation with clear understanding that it is part of the religion and this process continued till the present time. These sunan (singular sunnah) are absolutely authentic for they do not rely on individual to individual narratives, the hadiths, but the consensus of the entire generation in each layer from the Prophet (sws) to our generation.
If the Qur'an and the Sunnah are silent or the scholar wants to learn how the Prophet (sws) acted upon the Qur'anic guidance in that matter he turns to the Hadith literature. The scholars working in the field of hadith collected and compiled hadiths in the third century. These books are now readily available. There are many hadith works but covering the six canonical books (sihah sittah), Mu'atta of Imam Malik, Musnad of Imam Ahmad, Musannaf of Abd al-Razzaq and Musannaf of Ibn Abi Shaybah do not leave anything uncovered.
With the currency of digital books we can just run a search and find out all the ahadith in a given topic. Some of the brilliant softwares help us collate all the material scattered in the sprawling literature very easily.
Then there are works of the fuqaha who studied the material with a different angle. They not only report or receive a report but try to fit it in the overall structure of the shari'ah. Their works must also be consulted before one forms a view. At least one should study the major works of the famous schools of the law on a given matter.