Each hadith arrives with a chain of names meant to vouch for it
A hadith is a report of something the Prophet Muhammad said, did or silently approved. Attached to each in the developed tradition is an isnad, a list of the people who supposedly heard it and passed it on, link by link. Whole scholarly disciplines grew up around testing those chains.
The Arabic word simply means a report or account. Such reports first circulated orally after Muhammad's death, often without any stated source. Between the seventh and tenth centuries, collectors known as muhaddiths gathered them systematically, arranging them first by the authority they were credited to and later by topic. Over the following centuries specialists devised grades for judging them: sahih for authentic, hasan for good and da'if for weak.
The results matter enormously, because hadith rank as the second authority after the Quran and a large share of Islamic law is drawn from them rather than from scripture itself. It was not always so. According to the scholar Joseph Schacht, early generations leaned mainly on reports about Muhammad's companions and their successors, and it was al-Shafi'i, founder of one of the major legal schools, who insisted that a report from the Prophet outweighs anyone else's. The Muwatta of Imam Malik, often called the earliest written hadith collection, still blends the two: one edition counts 822 reports from Muhammad and 898 from others.
Different communities built different libraries. Sunni Muslims recognise six canonical books, with Sahih al-Bukhari and Sahih Muslim held in highest esteem, though Maliki jurists traditionally swap Sunan ibn Majah for the Muwatta. Shia Muslims favour reports transmitted through Muhammad's family, the Ahl al-Bayt, while Sunnis weigh narrations from any of roughly twelve thousand companions without regard to lineage. Those contrasting choices helped shape distinct approaches to Sharia.
Authenticity has been disputed from the start. Early groups including the Kharijites and the Mu'tazila limited or rejected hadith, and modern Quranists give them no religious authority. Western critical historians go further, generally arguing that much of the material reflects the legal, theological and political quarrels of the eighth to tenth centuries rather than the seventh. Most collections were written down long after the events they describe, roughly two to three centuries later for major Sunni works and four to five for Shia ones.
Source: Hadith
