Qiyas

Abu Hanifa al-Nu'man ibn Thabit (699–767 CE) founded the Hanafi school of jurisprudence, the most widely followed legal tradition in the Muslim world. A silk merchant turned scholar, he developed a method balancing scripture with reason, and died in Abbasid imprisonment.

Muhammad ibn Idris al-Shafi'i (767–820 CE) founded the Shafi'i school of jurisprudence and was the architect of Islamic legal theory. His Al-Risala established the first systematic framework for deriving law from its sources, resolving a crisis of conflicting legal opinions.