We do not base prohibitions on intentions or intuition; a prohibition applies only to what is certainly forbidden, otherwise it remains permissible. For example, manufacturing televisions is not forbidden even though most of what we see on them might be prohibited; the television is merely a device that can be used for both good and bad purposes, and the moral responsibility of the act lies with the user, not the maker.

Similarly, a knife can be used to kill or to slaughter according to religious law, and the difference lies in how it is used, not in the knife itself. You are responsible for designing something that is fundamentally permissible. If some people use it in an impermissible way, that is on them, and perhaps Allāh will replace them with those who use it otherwise. It is not required in your job to specify the type of usage.

The restaurant for which you will design some aspects is essentially a permissible building, like a hotel or a prison. If a hotel is used as a brothel, that is on the users; if a prison is used to unjustly imprison innocent people, that is the concern of the jailer, not the designer. The prohibition applies only if the designer intends to facilitate the forbidden act with their design as their intention will be attached to the forbidden act; otherwise, there is no prohibition.

Fatwā issued by Dr. Khālid Naṣr