Al-Risala is the best known work of al-Shafi'i, noted especially for its clear Islamic jurisprudence. In this work, al-Shafi'i outlines four different sources of Sacred Law (usul al-fiqh) and their relative importance in determining what God wills man to do. According to Al-Risala, the first source of Sacred Law is the Qur'an, which is to be consulted directly. Then, for specific matters that are not addressed in the Qu'ran, consideration should be given to the Sunnah, or the divinely inspired practice of the Prophet Muhammad. If no instances for settling a particular case could be found in the Qu'ran or the Sunnah, the third source suggested by Al-Risala is ijma' or scholarly consensus. Finally, if no consensus can be reached, qiyas -- reasoning by analogy to the first three sources -- is allowed.[1]
The first source of law covers those duties made clear in the Qur'an. For example, Al-Risala suggests that according to the Qur'an men must "perform the prayer, pay the zakat (alms tax), perform the pilgrimage, and observe the fast." On the other hand, men are forbidden from "adultery, [the drinking of] wine, eating [the flesh of] dead things and of blood and pork."
The Sunnah covers those duties which are required by the Qur'an, but whose methods are made clear only through the words and practice of Muhammad. Extending the examples cited for the first source, Al-Risala describes "the number of prayers [each day] and the [amount of] zakat and their time [of fulfillment]" as examples of issues that may be clarified through the Sunnah.
For those issues that are addressed by neither the Qur'an nor the Sunnah, the ulema (Islamic scholars) can be consulted in order to arrive at a consensus.
Finally, as a last resort, ijtihad (personal reasoning) may be used to seek the truth. This personal reasoning entails the use of analogy (qiyas) to relate a specific issue to something that has already been addressed by any of the other three sources of Sacred Law.[2]