What are the fixed rules for prohibiting things and matters in Islam, taking into consideration His — the Almighty’s — saying: "And do not say about what your tongues falsely describe, 'This is lawful and this is unlawful,'..." and the Prophetic Hadith: "The lawful is what Allah has made lawful in His Book, and the unlawful is what Allah has made unlawful in His Book, and what He has remained silent about is among that which He has pardoned," and the saying of the scholars: "The unlawful is that for which there is a severe threat [of punishment]"?

The root of the problem is confining prohibition to severe threats, which is incorrect. While a threat can imply prohibition, severity is not a condition for it, nor is prohibition limited to it. Ibn al-Qayyim mentioned many forms from which prohibition can be inferred, including: an explicit prohibition, an explicit statement of prohibition, a ban, denouncing the perpetrator, requiring expiation, and the phrase "it is not appropriate." Similarly, Sheikh Abdullah al-Judai' mentioned in "Taysir 'Ilm Usul al-Fiqh" various forms, among them: the explicit word for prohibition, negating permissibility, various forms of command to abstain, anything upon which a worldly or otherworldly punishment or threat is based, describing an act as a sin or major sin, describing it as aggression or injustice, likening the perpetrator to animals or devils, and naming an act after something forbidden that is known to be prohibited.

The piety of the imams in refraining from explicitly using the word "prohibition" does not mean permissibility; rather, it was a known convention among them. The terms "makrooh" (disliked/reprehensible) and "la yanbaghi" (it is not appropriate) were used by them for what is legally prohibited, unlike the later convention that restricts "makrooh" to what is not prohibited.

As for accusing some scholars of prohibiting what has no textual evidence or threat, this is incorrect, because the sources for ruling something as prohibited are wider than some imagine. Therefore, the questioner should attribute this to their own shortcomings, not to accusing scholars.

Regarding the beard, the Prophet (peace be upon him) commanded its growth and letting it hang. There is an explicit text that Allah Almighty commanded it.

As for the prohibition of smoking, it is inferred from it being among the harmful foul things, based on Allah's saying: "{and prohibits for them impure things}." This does not contradict describing onions and garlic as foul, because their foulness refers to a temporary odor, not harm.