أربعة: كتاب الله تعالى، وسنة رسوله، وإجماع الأمة، والقياس
The four sources are the Book of Allah, the Sunnah of His Messenger, consensus, and analogy.
These are not merely four labels. Their authority, methods of interpretation, and relationship to other evidence form the structure of legal inference.
The Qur'an and Sunnah supply scriptural evidence; consensus concerns agreement among qualified jurists; and analogy extends an established ruling to a new case through a legally effective common cause. Each operates under its own conditions.