What are the three classifications of Hadiths and what do they mean?

Answer 1

The Hadith literature was aggregated 150 years after the death of Muhammad and the major Islamic scholars or 3ulemaa (علماء) noted that numerous things crept into the Hadith literature that were clearly not from Muhammad's life or his views including: Zoroastrian Proverbs, Jewish Psalms, provisions for increasing the flour content of cookies (you cannot make this stuff up), etc. Recognizing the prevalence of these forgeries, there are three classifications of Hadith literature in Traditional Islam developed: da'if (ضائف) - weak, hassan (حسن) - good, and sahih (صحيح) - pure/healthy. They classified the Hadiths by their chains to transmission, the amount of different transmission methods that they went through, and how likely they would have been to have occurred.

For example, the Hadiths listed above (Zoroastrian Proverbs et al.) were seen to be da'if - weak. The Hadith collectors worked with 300,000 Hadiths and saw less than 10% of them to be sahih - pure and therefore worth following. Those collections became named "Sahih" followed by the collector's name, i.e. Sahih al-Bukhari or Sahih al-Muslim, etc.