The Risāla by al-Shafi'i (d. 820), full title Kitab ar-Risāla fī Uṣūl al-Fiqh (Arabic: كتاب الرسالة في أصول الفقه, "The Book of the Treatise on the Principles of Jurisprudence"), is a seminal text on the principles of Islamic jurisprudence.
Khadduri rearranged those chapters because they did "not appear to fit into the logical order of the book.
The primary sources of law attributed to Shafi'is book are the Qur'an and the prophetic tradition.
Most Muslim commentators have also referred to Shafi'is sections on consensus and analogical reason as comprising legal sources.
[5] Later followers of his school considered this to be practically impossible, and thus expanded upon the definition.