Bismillahi Al-Rahmani Al-Rahim

The Basic Sources of Law:
Imam Ahmad’s usul al-fiqh

The founders of the four mathabs, Imams Abu Hanifa Al-Nu`man, Malik bin Anas, Muhammad bin Idris Al-Shadi`i, and Ahmad bin Hanbal (may Allah be pleased with them all), were not arbitrary in forming their legal opinions. Each one of these imams had a legal theory regarding legal sources of law, the principles for interpreting these sources, and an actual methodology for applying these principles.

The four schools agree one the use of Qur’an, hadith, scholarly consensus (ijma`), and analogical reasoning (qiyas). But even though the schools agree on the use of these four sources, there are slight differences in how each one is used. In addition, each school adds additional sources to this list.

This leads to the obvious conclusion that differences the usul lead to differences in the furu`.

It also leads to a less obvious conclusion that we cannot determine which opinion is strongest until we have determined which usul is strongest. This is not always a trivial task.

As for the usul of the Hanbali mathab, the basic list, since at least the times of Ibn Qayyim Al-Jawziya, includes five:
1.      Al-Nass which includes the Qur’an and accounts from the Prophet (Allah bless him and give him peace) that are rigorously- or well- authenticated (respectively: sahih, hasn)
2.      A fatwa from one of the Companions when the other Companions (Allah be well pleased with them one and all) are not known to differ with it
3.      When there is a difference of opinion between the Companions (Allah be well pleased with them one and all), then whichever one is closest to the Qur’an and sunna; if it was not clear which opinion was closest, then he would mention that there is a difference of opinion without being convinced [of the superiority of any particular one]
4.      Hadiths that are mursal, where one of the tabi`in (someone who met at least one of the Companions (Allah be well pleased with them)) ascribes a hadith to the Prophet without mentioning the narrator(s) between himself and the Prophet (Allah bless him and give him peace);
Hadiths which are weakly authenticated (da`if) when there is nothing to refute it, however there is disagreement concerning the meaning of “dha`if” here
5.      Analogical reasoning (qiyas)

But as Imam Muhammad Abu Zahrah points out in his book concerning Imam Ahmad, the picture is a just bit more complicated than that. As a minimum, we can add the following to the list:
6.      Al-Istishab, which is projecting a known ruling into the past or present
7.      Al-Masalih Al-Mursala, which looking at the public interest
8.      Al-Thar`i, which is giving something the ruling of that which is leads to

This, in sha Allah, gives a very general and simplified picture of Hanbali usul. For more information on individual topics, please consult an Arabic Hanbali usul reference, or see Kamali’s Principles Of Islamic Jurisprudence.