 Because some hadith include questionable and even contradictory statements, the authentication of hadith became a major field of study in Islam.In its classic form a hadith has two parts — the chain of narrators who have transmitted the report (the "isnad"), and the main text of the report (the "matn").Individual hadith are classified by Muslim clerics and jurists into categories such as "sahih" ("authentic"), "hasan" ("good") or "da'if" ("weak").