Hukm is communication of Allah (Qur'an, sunnat, and other sources of Law such as ijma and qiyaas) relating to actions of humans.

Classification of hukm shara’i

Hukm shara’i can be classified in three categories: injunctive, hukm takliifi; stipulatory, hukm wadhai; and optional, hukm takhyiiri. Hukm taklifi is primary whereas the other two are seconday to it. Hukm taklifi ordains an action, al iqtidhau and takes the following forms: wajib, manduub, haram, makruuh, mubaah, and aziimat & rukhsah.

Waajib

Waajib is considered the most important hukm taklifi. The definition of the obligatory, waajib, varies in different schools. The Shafi’i and Hanbali schools consider waajib the same as faradh. In the Hanafi school the faradh is stronger than the waajib.

Waajib can be restricted, muqayyad, or open-ended, mutlaq. There are several types of restrictions: restriction by time, muqayyad bi al zaman; restriction by amount or quantity of performance, muqayyad bi al taqdir; restriction by specification of the required performance or action, muqayyad bi ta'ayin al matluub; and restriction by specification of the person required to perform the action, muqayyad bi al mutaalab bihi.

Some obligations must be performed at a specified time whereas others have latitude in time. Delaying an act that has a wide latitude of time is not blameworthy as long as it is performed before the expiry of the extended time period; it is however recommended to perform acts early. Expiry of the assigned time for the act does not nullify its obligation. It still has to be performed.

If the amount of expected performance is not specified, any amount of work will suffice to discharge the obligation.

Injunctions may be general like good treatment of parents, birr al walidayn, without specifying specific actions, in that case any good act discharges the responsibility.

Individual obligations, fardh ‘aini, cannot be delegated.  Performance of a collective obligation, fardh kifai, by any member of the community absolves the rest from sin. However only those with the necessary competence can perform the collective obligations. The rest are not obliged even if they are members of the community.

Manduub

Recommended, manduub, is a type of hukm taklifi that is also called sunnat or masnuun, nafilat, mustahabb, tatawu'u, ihsaan, or fadhiilat.

The manduub has got the following levels of excellence: confirmed, sunnat muakkadat; not confirmed, sunnat ghayr muakkadat. The sunnat muakkadat is what the Prophet used to carry out continuously and left it only on rare occasions.

An act can be manduub when considered in isolation like marriage. However it can be waajib if considered generically for example the whole community cannot choose not to marry.

Haram

Prohibited/unlawful, haraam, is a type of hukm taklifi. It is defined as omission of the waajib or commission of the haraam. It can be intrinsically prohibited or extraneously prohibited. The intrinsically prohibited acts, muharram li dhaatihi, are prohibited on their own merit. The extraneously prohibited acts, muharram li ghayrihi, are prohibited for a reason extrinsic to the action. Some jurists consider an extraneously prohibited valid but accompanied by ithm. Others consider such an act as invalid.

Committing the prohibited can either be kufr; a major sin, kabir al ithm; or a minor sin, saghir al ithm. Repetition of a minor sin turns it into a major sin.

The original position for all human acts is permission, al asl fi al umuur al ibaahat, and prohibition, al hurumat is the exception. Thus textual evidence is required to prove prohibition but is not required to prove permission. The situation is reversed in sexual matters in which the original position is haram, al asl fi al abdhaai al hurmat. Permission is the exception and requires textual evidence.

Only Allah can make something haraam. Haraam is prohibited because it is impure and harmful. An act that leads to haraam is also haraam. An act that aggravates disease is haram. An act that cures disease is waajib. For inconclusive matters what leads to bad or evil is makruh and what leads to good is manduub. A general principle is that the halaal is clear and the haraam is clear and between the two are inconclusive matters, mutashaabihaat.

Makruuh

A disapproved/offensive/reprehensible, makruuh, is an act that is discouraged by the Law giver without compulsion. It is better to avoid the makruuh. The makruuh is of two types: makruuh tahriiman and makruuh tanziihan. The former is based on definitive evidence, daliil qat'i, and is closer to haraam. The latter is based on probable evidence, daliil dhanni. The makruuh is an introduction to the haraam and must therefore be avoided. An act that is makruuh for a specific individual or situation can be haraam if generic.

Rewards and punishments for various acts

The classification of acts can best be understood from the consequences of doing them or not doing them:

Aziimat & rukhsat

Aziimat is also called strict application or application of general rules. Rukhsat is also called dispensation, relaxation, exemption, or application of the rules to specific situations..

‘Aziimat is a general obligation, al azimat huwa hukm takliifi li al umuum. Rukhsat is an exemption due to a necessity, dharurat. ‘Aziimat is general, kulliyat, whereas rukhsat is an exception, istithnau. Rukhsat is when what is normally forbidden is allowed or when an obligation is omitted.

Rukhsat can take the following three shapes: permitting the forbidden, ibaahat al muharram, under necessity, dharurat; permitting leaving the obligatory, ibahat tark al waajib; and making exceptions to a general ruling, istithnau 'an al qaidat al aamat.

The regal ruling on rukhsat is either mubaah or wajib. In the former the human is free to enjoy the exemption or not. Under the latter the human is obliged to make use of the dispensation even if he feels he need not do so such as eating dead human flesh when faced with starvation.

Exemptions are always given for individuals and the not the whole community. For example an individual may be exempted from enjoining good, amr al ma'aruf, or forbidding evil, nahy al munkar, but no such exemption can be made for the whole ummat.

In general it is better to be on the safe side by avoiding taking exemptions unless on very sure and valid grounds, ihtiaat tajannub al rukhas.

Validity, sihhat & Legal defectiveness, butlan: Acts that are not valid under the law can be classified as null and void, baatil, or irregular, faasid. An act is baatil when a pillar, rukn, is defective. It is faasid when a condition, shart, is defective.

In ibadaat, baatil is the same as faasid. In mu'amalaat, an act deemed faasid can have some legal effect and is not baatil. It can become valid when the cause of the irregularity is removed. This is because the legal implications are from the consequences of the act and not the act itself.

The baatil is what is prohibited because of its essence, al baatil ma nuhiya ‘anhu li dhaatihi. The faasid is what is prohibited because of one of its attributes, al faasid ma nuhiya ‘anhu li wasfi fiihi.