What is the ruling on an engineer working on a project that includes both permissible facilities (residential and medical) and impermissible facilities (tourism and interest-based) within the same urban development, and is it permissible to design four-star hotels that do not serve alcohol in similar projects, and is it permissible to develop work and management systems and assist companies that engage in both permissible and impermissible activities without directly interfering with the impermissible?

The work of an engineer falls into three categories: First, prohibition, if the participation is in forbidden constructions such as banks and taverns, as this falls under cooperation in sin and aggression. Second, permissibility, if the participation is in lawful or permissible constructions such as mosques and dwellings. Third, if the participation is in constructions that combine both lawful and unlawful elements, then it is not permissible for him to participate in planning or supervising the forbidden areas, but it is permissible for him to participate in what is permissible among them. This ruling applies to accountants, laborers, and others. If a person fears that he will not be able to avoid the forbidden, then he must leave this job.