What is the ruling on designing signs for barbershops and women's beauty salons? Is it permissible based on the permissibility of the thing itself, or is it impermissible due to the impermissibility of other things?

The fundamental principle is that working in advertising is permissible, based on the permissibility of buying and selling, as Allah Almighty says: "But Allah has permitted trade and forbidden interest." However, if advertising is associated with something unlawful, or if it aids in something unlawful, then it is forbidden.

Therefore, if the work of the shops for which the advertising is designed is unlawful, it is not permissible to design for them. But if their work is lawful, then it is permissible.