Al-Risala, authored by the venerable Imam al-Shafi'i, stands as the cornerstone of Usul al-Fiqh (the principles of Islamic jurisprudence). It is the first systematic work to articulate the methodology for deriving Islamic law. In this seminal text, al-Shafi'i masterfully establishes the four primary sources of legislation: the Qur'an, the Sunnah of the Prophet, scholarly consensus (Ijma), and analogical reasoning (Qiyas). He meticulously defines their hierarchy and the principles of their interpretation and application. This work provided a foundational framework that has shaped all subsequent Islamic legal thought, making it an indispensable resource for scholars and students.