**The Four Books** (الكتب الأربعة) refers to the the four canonical hadith collections of Shia Islam, compiled between the 4th and 5th centuries AH. Authored by Shia scholars al-Kulayni, Ibn Babuya, and al-Tusi, they are the most authoritative sources of hadith, jurisprudence, and theology for Shia scholarship. - [[Kitab al-Kafi]] - [[Man la Yahduruhu al-Faqih]] - [[Tahdhib al-Ahkam]] - [[al-Istibsar]]