The asl (fundamental principle) concerning commands in the Book and the Sunnah is that they are indicatie of a wujoob (obligation), except if there is an eviidence to indicate to it being mustahabb (recommended) of mubaah (permissible) The asl concerning prohibitions is that they are indicative of tahreem (forbidance), except if there is an evidence indicating it being makrooh (hated).
The asl governing kalaam (speech) is that it is to be taken upon its haqeeqah (literal sense). So it is not to be turned away from it to its majaaz (figurative meaning) - if we accept this - except when it is impossible to employ its haqeeqah (literal meaning)
Al-Haqaaiq (literal meanings) are of three types: [i] shariyyah (that which is defined by the Shareeah), [ii] lughawiyyah (that which is defined by language) and [iii] urfiyyah (that which
is defined by customary useage).
So whatever ruling the Shaari (Lawgiver) has defined, then it is obligatory to return it to the Shareeah definition. However, what the Lawgiver has ruled, but not defined, sufficing by its apparent linguistic meaning, then it is obligatory to return it to its linguistic meaning. But whatever has not been defined, neither in the Shareeah, nor in the language; then it is obligatory to refer it back to the habits of the people, and their customary useage. The Shaari (Lwgiver) may clearly specify to return these matters to urf (customry useage); such as commanding the good, living well with ones wife, and other similar matters.
So memorise these usool concerning which the faqeeh stands in need of in all his dealings of fiqh.
From the texts of the Book and the Sunnah are those which are aam (general); which is defined as that word which is inclusive of many ajnaas (catagories), anwaa (types) and afraad (individuals). This majority of the texts are of this nature. Other texts are khaass (specific), and are indicative of only some catagories, types and individuals. Thus, if there does not exist any contradiction between the aam and the khaass texts, then each of them are independantly acted upon. However, if a contradiction is presumed, then the aam is specified and deliniated by the khaas.
From the texts are the mutlaq (absolute) and the muqayyad (restricted) ones. It is restricted by a description or a reliable restriction. Thus, the mutlaq is restricted and qualified by the muqayyad.
And from the texts are the mujmal (comprehensive) and mubayyan (explicit). Whatever the Lawgiver has made comprehensive in one place, yet made it explicit in another, then it is obligatory to return to what the Lawgiver made mubayyan (explicit). Many of the rulings in the Quraan are mujmal (comprehensive) in nature, but have been explicitly explained in the Sunnah. So it is obligatory to return to the bayaan (explicit clarification) of the Messenger sallallaahu alayhi wa sallam, since he is the clear explainer from Allaah.
Similar to this are the texts that are muhkam (equivocal and singular in meaning) and those that are mutashaabih (unequivocal and open to more than one meaning). It is obligatory to understand the mutashaabih in the light of those texts that are muhkam.
Amongst the texts are the naasikh (abrogating) and the mansookh
(abrogated) The abrogated texts in the Quraan and the Sunnah are few in number. Whenever there is the possibility of harmonising two texts, with the possibility of each one being acted upon in its own particular circumstance, then it is obligatory to do so. One may not turn to abrogation, except with a text from the Lawgiver, or an apparent contradiction between two authentic texts concerning which there is no possible way to reolve this contradiction such that each text is acted upon in its own particular circumstance. in this case, the later text abrogates the earlier one. However, if it is impossible to determine which is the earlier text and which is the later, we then turn to other means of tarjeeh (prefering one text over another). For example, when there is an (apparent) contradiction between the Prophet sallallaahu alayhi wa sallams statement and his action, then precedence is given to his saying. This is because his statement represents either a command or a prohibition to his Ummah, whereas his action is, in this case, interpreted to be something particular to him alone. So the
khasaais (particular and unique rulings) pertaining to the Prophet sallallaahu alayhi wa sallam are actually based upon this asl (fundamental principle).