al-Jassas

Abu Bakr Ahmad ibn Ali al-Razi, known as al-Jassas ("the plasterer," after a trade connected to his background), was a leading jurist of the Hanafi school — one of the four main Sunni schools of law (madhhabs) — who worked in tenth-century Baghdad. Sources place his birth around 305 AH (c. 917 CE), traditionally at Rayy, near present-day Tehran, where he is said to have begun his studies before traveling onward for advanced learning.

Reports place him in Baghdad as the close student of Abu al-Hasan al-Karkhi, then a leading figure among the Baghdad Hanafis, and the tradition holds that he succeeded al-Karkhi as head of that circle; the tradition also reports that he travelled to Nishapur, a center of hadith scholarship, under al-Karkhi's guidance. The exact year he reached Baghdad is uncertain — one report has him arriving around 325 AH (c. 937 CE) as a young man. He is remembered as cautious about power: al-Khatib al-Baghdadi reports that he twice declined appointment as chief judge (qadi al-qudat), preferring teaching and scholarship.

He is best known for two works. Ahkam al-Qur'an ("Rulings of the Qur'an") systematically derives legal conclusions from Qur'anic verses along Hanafi lines, and al-Fusul fi al-Usul is an important early treatise on usul al-fiqh — the theory and method of deriving law. Later writers note that he was influenced by Mu'tazili thought (a rationalist theological current); some read this as a clear inclination, while others read his positions as more nuanced — a matter of debate, not settled fact. He died in 370 AH (c. 980-981 CE), by most reports at Baghdad (one source instead places his burial at Khwarazm).