What is the ruling on money acquired from taking a percentage of a sum for a project that is transferred to a third party after all its details have been agreed upon with the client?

It is permissible for a joint employee (ajeer mushtarak) to accept work and then commission someone else to perform it for a lower price, so that they can take the difference, provided they adhere to the employer's conditions regarding the quality of the work, and provided the employer did not stipulate that the employee must perform the work themselves. Precedents and custom serve in place of a stipulated condition.