How is the legal ruling for actions determined (Fard, Wajib, Sunnah, Mustahabb, Mubah), and who established these classifications?

1. Allah alone possesses the right to legislate, command, prohibit, and rule. Glorified be He, He has denounced those who take a legislator other than Him.

2. Allah Almighty has obligated obedience upon His servant in all circumstances. The servant performs what is commanded of him and refrains from what is forbidden to him. This is known as the Shariah ruling (Al-Hukm Al-Shar'i).

3. The five categories of obligatory Shariah rulings (Al-Ahkam Al-Taklifiyah) are: Wujub (Obligation), Nadb (Recommendation), Tahrim (Prohibition), Karahah (Dislike), and Ibahah (Permissibility). These have been enumerated through inductive reasoning.

4. There are multiple ways to determine if something is obligatory, recommended, permissible, and so on. These include:

Wujub (Obligation): This is identified by the four forms of the imperative (the imperative verb, the jussive present tense verb with the 'lam al-amr', the imperative noun-verb, and the verbal noun acting as its verb's substitute), explicit statements of obligation (wujub), fard (compulsory), or katb (prescribed), any style indicating obligation, and the consequence of blame and punishment for omission.

Nadb (Recommendation): This is identified by an explicit command accompanied by a contextual indicator that shifts it from obligation to recommendation, explicit statements of sunnah (prophetic tradition) or preference (afdhaliyyah), and any expression indicating encouragement.

Tahrim (Prohibition): This is identified by the absolute form of negation, the use of the word 'tahrim' and its derivatives, explicit statements of impermissibility or negation of lawfulness, the consequence of punishment for the action, the imperative form indicating a request to abandon something (e.g., "abstain," "forsake"), and the phrase "it is not for you/us."

Karahah (Dislike): This is identified by the word "kariha" (disliked) and its derivatives, the prohibitive phrase "do not do" accompanied by a contextual indicator that shifts it to dislike, and the Prophet's (peace be upon him) statement, "As for me, I do not do it."

Ibahah (Permissibility): This is identified by the use of the word "ahalla" (made lawful) and its derivatives, the removal of blame (raf' al-janah), the removal of hardship (raf' al-haraj), explicit statements of no sin, contextual indicators that shift imperative forms from obligation and recommendation to permissibility, the words of permission (idhn) and forgiveness (afw), silence regarding prohibition, and the Prophet's (peace be upon him) approval of an action during the time of revelation.