Kitab al-Kafi

Muhammad ibn Yaqub al-Kulayni worked on Kitab al-Kafi for roughly twenty years, completing it in Baghdad not long before his death in 941 CE, during the early decades of the Minor Occultation, the period in which Twelver Shia Islam's Twelfth Imam was held to be in hiding and communicating only through a series of deputies.

The book divides into three parts. Usul al-Kafi, the largest and most cited, gathers hadith on theology and doctrine: the nature of God, prophecy, the status and authority of the Imams, and the principles by which a believer is meant to reason about faith. Furu al-Kafi turns to practical law, covering ritual purity, prayer, fasting, pilgrimage, marriage, inheritance and commercial transactions in the detailed case-by-case style typical of early Islamic legal literature. Rawdat al-Kafi, the shortest section, is a miscellany of sermons, letters and narrative reports that do not fit neatly under either heading. Across the whole work al-Kulayni assembled something close to sixteen thousand individual hadith, each carried by its own chain of transmission back through earlier narrators to one of the Imams, making Kafi as much a record of how Twelver Shia scholars of his generation understood authoritative transmission as it is a statement of doctrine and law in its own right.

Kafi was the first of what later tradition grouped together as the Four Books, joined over the following century and a half by Man La Yahduruhu al-Faqih, Tahdhib al-Ahkam and al-Istibsar. Its early completion and comprehensive scope made it the most frequently cited of the four in later legal and theological writing, and it remains the starting point for seminary study, the hawza, in Twelver Shia centers of learning today. That status has not made it uncontested. Twelver scholars have long disagreed over how many of Kafi's roughly sixteen thousand hadith can be treated as reliably authenticated, with estimates ranging from a small fraction judged fully sound (sahih) by the strictest chain-of-transmission standards to a much larger number accepted as usable for law or doctrine under looser criteria.

The disagreement tracks a broader split between the Akhbari school, which favors reading the Four Books more directly as reliable in their transmitted form, and the dominant Usuli school, which treats Kafi as raw material to be evaluated and reasoned over using the tools of jurisprudence (usul al-fiqh) rather than accepted wholesale. Both approaches keep Kafi at the center of the argument rather than settling it.