What is actions of a mukallaf?
Islam commands Muslims to do certain things, to avoid certain things, and leave others to their own choices. The categories of actions of a mukallaf is called “Af’al al-Mukallafin”. There are five categories:
1.Wajib 2. Mandub 3. Mubah 4. Makruh 5. Haram.
As can be seen, scholars use slightly different terms in categorizing the actions of a mukallaf. Due to their varying classifications, they were considered to have introduced completely different approaches even though scholars approach the matter with the same spirit, caution and care. This situation has led to some misconceptions and been interpreted, especially by the common people, as a clash among madhahib. Whereas, the important point is to not overlook the fact that the only difference between them is the terms used for classification.
For example, Hanafis consider ritual walking (say) during pilgrimage as wajib since there is no clear command in the verses, while Shafi’is, Malikis, and Hanbalis consider this act of worship fard due to its significance. While the Hanafi School considers witr prayer as wajib, the Maliki, Hanbali and Shafi’i schools rule it to be a Sunnah of the Prophet. If we take a closer look, the witr prayer is actually not considered by these three schools under the same category as the rest of the Sunnah prayers. It has been described as an emphasized Sunnah (that is not fard), which is performed after the night prayer (‘Isha).
 The five-category classification made by Shafii, Maliki, and Hanbali scholars is used in this book. The term wajib used by Shafii, Maliki, and Hanbali jurists generally corresponds to fard and wajib in Hanafi School, while the term mandub consists of sunnah and mustahab.
Source: Fiqh1 (According To The Shafi’i School Of Islamic Law), Erkam Publications