Know that the slave/servant is tribulated between obeying Allah (the most high) thereby being rewarded and between disobeying Him and being punished.
Tribulation is related to that which is permissible and impermissible, in terms of both performance and non performance.
Therefore it is necessary for an exposition of the types of legislated and non legislated acts, along with an explanation of their meanings and rulings so that it may be easier for the student to fully understand them.
So we say and with/through Allah is success:
The legislated actions are of four categories:
1- Obligatory (fard)
2- Compulsory (wajib)
3- Recommended (sunnah)
4- Desirable (mustahab)
They are followed by: permissible (mubah)
The non legislated actions are if two categories:
1- Unlawful (muharram)
2- Disliked (makruh)
They both are followed by: invalidator (mufsid) of an act which has been begun
In total there are eight categories.
As for the Fard: it is that which is established by a definitive proof in which there is no doubt (shubha)
The ruling for it is: reward for its performance, punishment for non performance without a reason, disbelief for denying regarding that which there is agreement.
As for the Wajib: it is that which is established by a proof in which there is some doubt.
The ruling for it is: similar to that of the fard in terms of action and not belief, such that its denier does not commit disbelief
As for the Sunnah: it is that which the Prophet (s) performed habitually leaving it only once or twice.
The ruling for it is: reward for its performance, blame for its non performance in the sunnahs of guidance.
As for the Mustahab: it is that which the Prophet (s) performed at times and left at other times, and that which is beloved to the early Muslims (salaf).
The ruling for it is: reward for its performance and no blame for it being left
As for the Mubah: it is that which the slave has a choice in between performing and leaving.
The ruling for it is: neither reward nor punishment for its performance or leaving.
As for the Muharram: it is that regarding which the prohibition is established without any conflicting evidence.
The ruling for it is: reward for its being left for Allah (azza wa jall), punishment for its performance, disbelief for regarding as permissible that which there is agreement as being unlawful.
As for the Makruh: it is that regarding which the prohibition is established with the presence of a conflicting evidence.
The ruling for it is: reward for it being left for Allah, fear of punishment for its performance, not being disbelief to regard as lawful.
As for the mufsid: it nullifies the action which has been begun
The ruling for it is: punishment for its deliberate not accidental performance
Then know that the prayer encompasses the first four in terms of from the sacred law, and the last four are found in it by nature
Therefore it is necessary to detail each category in a succinct but comprehensive way organised into eight chapters in order to make it easy for the believers.
The reason for why humans feel that they are undergoing trials and tests is because of the choice that they have been given in being obedient or disobedient to the divine commands. al-Jawhar
It should also be noted that this world is a place of being tested and tribulated and is not our final abode, unlike the dealing of many with this world as if it is everlasting and that they will never leave it.
 Meaning that there are times when an obligatory (fard) action can be left or changed, examples of this are a traveller not having to fast and shortening the prayer.
 This does not apply to the differences of opinion of the scholars about whether certain acts are obligatory (fard) or not. Al-Jawhar
 Imam al-Nablusi mentioned in al-Jawhar that this definition also includes that which was habitually practised the four khalifah’s (Allah be pleased with them). This definition was also supported al-Luknawi who said in Tuhfah al-Akhyar (p.84): ‘Many of our companions such as the authors of al-Hidayah, al-Tahrir, Bahr al-Ulum, authors of al-Kashf and al-Tahqiq, al-Tabyin, Islah wal-Idah, Mirqat al-Usul, al-Muhit, al-Khulasah, al-Nahr, Abu al-Yusr al-Bazdawi, al-Ta
htawi and others defined a recommended act (sunnah) in a manner that it includes the practice of the khalifah’s, making it such that the one who leaves it is blamed. Rather the author al-Binayah regarded leaving it as being punishable’.
 Leaving the emphasized recommended acts (sunnah al-muakkadah) is close to being unlawful, and this is also the status of the prohibitively disliked act (makruh tahrimi). The scholars mentioned that leaving the emphasized sunnah may lead to being deprived of things such as intercession in the next world. Tuhfah al-Abrar (p.87-88), Rad al-Muhtar (6/337)
 Meaning the emphasized recommended acts (sunnah al-muakkadah)
 This definition is also mentioned in al-Tabyin (1/77), al-Hidayah (2/92), al-Inayah (2/92) and Majma al-Anhur (1/139). Imam Ibn Abidin said in Minhah al-Khaliq (2/278) echoing that which was mentioned by Ibn Nujaim in al-Bahr al-Raiq (1/29): ‘Know that the scholars of usul do not differentiate between mustahab and mandub…that which was not habitually performed is mandub and mustahab, even if it was not performed after its being encouraged as mentioned in al-Tahrir. According to the jurists (fuqaha): mustahab is: that which was performed by the Prophet (Allah bless him and give him peace) at times and left at other times. Mandub is: That which was performed once or twice to teach its being permissible as mentioned in Sharh al-Nuqayah. Ibn Nujaim said in Kitab al-Taharah:…the preferred view is that of the scholars of usul’.
 Al-Nablusi mentioned in al-Jawhar that this applies even if it was not practised by the Prophet (Allah bless him and give him peace). Also what is meant by the term salaf are the early Imams such as Abu Hanifah and his students (Allah be pleased with them all).
Imam al-Nablusi’s definition of the term salaf is very interesting and is overlooked by many of those who use the term. This is because the salaf had numerous differing understandings of Islamic law which resulted in different schools of law (fiqh). Therefore if we say that we follow the salaf we should clarify which of the schools of the salaf we follow. Is it the school of Kufah which developed over time into the hanafi madhab, or the school of Madinah which developed into the Maliki madhab? If one does not specify which school of the salaf they follow it would be illogical as we know that the salaf in some instances had a varying number of views on one legal issue, which it would be impossible for a person to implement all at once.
 Al-Luknawi said in Tuhfah al-Abrar (p.91-92): ‘To conclude, the leaving of the sunnah in terms of belittling or mocking even it be from the zawaid is disbelief. Leaving it deliberately but not by way belittling is prohibitively disliked (makruh tahrimi) being a sin and deserving of blame if it is an emphasized (mukkadah) sunnah, it makes no difference if it is the sunnah of the Messenger (Allah bless him and give him peace) or of companions (Allah be pleased with them)’.
 It is that which the legally responsible person may perform or leave without any consequence of reward or punishment. It could also be defined as that which the person has a choice whether to perform or not. Al-Jawharah (2/280), Dur al-Mukhtar and Rad al-Muhtar (6/336)
The mubah maybe performed with an accompanying intention which would make it something rewardable or sinful. An example would be to eat with the intention of having enough strength to worship Allah (the most high). Likewise the wearing of fine clothing although permissible may become a sin if worn with the intention of arrogance and feeling of superiority over others. Al-Durar al-Mubahah (p.8-9), al-Jawhar
 Meaning a conflicting evidence which would indicate to that action being permissible
 Meaning the conflict of two evidences, one which indicates it to be permissible, the other which indicates to it being unlawful. Makruh tahrimi is closer to the unlawful (haram) due to this conflict of evidences where the evidence for it being unlawful is given precedence and therefore it is necessary for it to be left. Al-Ikhtiyar (5/413), Hasan al-Dirayah (4/95)
As for the disliked (makruh tanzihi) the one who performs it is not sinful, however one is rewarded for avoiding it. Not performing a disliked (makruh tanzihi) act is preferable. Rad al-Muhtar (6/337)
 What this means ‘by nature’ is that a human beings nature is to be forgetful or to be lazy, such that these two traits sometimes affect the performance of the prayer. Therefore ones nature of being lazy may lead to performing something in the prayer which is disliked etc. al-Jawhar