What is the ruling on taking a commission (tip) in exchange for giving a job to one person over another?

Paying money as a 'makarama' (a generous gesture or favor) between contracting parties is not permissible if its aim is to seize the rights of others. If a person pays money to an agent to obtain more than his rightful share of goods, land, or a project, then he is considered a briber, and the recipient a bribed party, and both are cursed.