Is it permissible to take a commission from painters in exchange for recommending them to work on contractors' projects, knowing that I help them succeed in their work?

It is permissible to take commission from painters in two cases: First, if your work is that of a broker, finding them clients. Second, if the commission is in exchange for assisting them in their work, which falls under the category of hiring (ijara). However, taking commission for influence (interceding for them with contractors) is not permissible unless you provide a service that deserves compensation or if it is a voluntary gift from them without any condition from you. This applies if you work independently. If you are employed by a specific entity, it is not permissible for you to take commission from its clients unless it is outside the scope of your defined work and outside official working hours.