What rules did the writers of the six authentic books (Sihah Sitta) apply to ensure the authenticity of Hadiths?

Mark scheme

Marking points from the official mark scheme (May/June 2014). The mark or mark type is shown in brackets.

1. [10] The writers of the six authentic books applied a very strict criteria in selecting the Hadiths for their books could be a simple start to this answer. Candidates need to give accurate information about the methods they employed of scrutinising isnad and matn. To get to the higher levels candidates will also need to write in some detail about how the compilers compared the body (matn) of the Hadith with reason, the Qur'an and other Hadiths to ensure that it agreed with the main Islamic principles. The importance of the chain of narrators (isnad) being unbroken could well be mentioned as well as the need to ensure that the narrator was of a sound mind, with a good memory and exemplary moral character. Examples of narrators going about collecting Hadiths could also be cited in well developed responses.
2. [4] This is an evaluative answer and candidate's responses should reflect their understanding of why it was deemed important to catalogue authentic Hadiths by the writers and perhaps reflect upon what could have been the possible dangers of not doing so.