Explanation

Hadith are classified by authenticity. Sahih (authentic): unbroken chain of reliable narrators, consistent text. Hasan (good): slightly weaker chain but acceptable. Daif (weak): problems in chain or text.

Major hadith collections: Sahih Bukhari and Sahih Muslim (most authentic), plus Sunan Abu Dawud, Tirmidhi, Nasai, and Ibn Majah (the Six Books).

Scholars examine isnad (chain of narrators) and matn (text content). Each narrator must be trustworthy, have good memory, and chains must connect properly.