5. Sources of Islamic Law (Usul al-Fiqh) — Detailed

Primary Sources

The Qur'an — the literal, uncreated word of Allah revealed to Muhammad (PBUH), the first and supreme source.
The Sunnah — the sayings (Qawli), actions (Fi'li) and tacit approvals (Taqriri) of the Prophet (PBUH).
Ijma — consensus of qualified Mujtahids of an era (see Procedure of Ijma, Theme VII).
Qiyas — analogical reasoning extending a known ruling to a new case sharing the same effective cause ('Illah).

Secondary/Supplementary Sources

Istihsan — juristic preference for public benefit over strict analogy in exceptional cases.
Maslahah Mursalah — unregulated public interest not directly addressed by a specific text.
'Urf — custom, so long as it does not contradict the Shariah.
Istishab — presumption of continuity.
Sadd al-Dhara'i — blocking the means to a prohibited end.

Qur'anic Evidence

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يَا أَيُّهَا الَّذِينَ آمَنُوا أَطِيعُوا اللَّهَ وَأَطِيعُوا الرَّسُولَ وَأُولِي الْأَمْرِ مِنْكُمْ ۖ فَإِن تَنَازَعْتُمْ فِي شَيْءٍ فَرُدُّوهُ إِلَى اللَّهِ وَالرَّسُولِ

اردو: اے ایمان والو! اللہ کی اطاعت کرو، رسول کی اطاعت کرو اور اپنے اولی الامر کی بھی۔ پھر اگر کسی معاملے میں جھگڑا ہو تو اسے اللہ اور رسول کی طرف لوٹاؤ۔

English: "O you who have believed, obey Allah and obey the Messenger and those in authority among you. And if you disagree over anything, refer it to Allah and the Messenger."

— Surah An-Nisa 4:59

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Hadith Evidence — Mu'adh ibn Jabal's Dialogue

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When sent to Yemen as judge, the Prophet (PBUH) asked Mu'adh how he would judge. He replied: "By the Book of Allah." "And if you do not find it there?" "By the Sunnah of the Messenger of Allah." "And if you do not find it there?" "I will exercise my own reasoning (Ajtahidu ra'yi)." The Prophet (PBUH) approved, saying: "Praise be to Allah who has guided the messenger of the Messenger of Allah to what pleases the Messenger of Allah."

— Sunan Abu Dawud 3592; Sunan al-Tirmidhi 1327 (al-Tirmidhi himself noted the chain is not strongly connected; jurists still cite it because its content is corroborated by the Companions' wider practice.)