What is the ruling on a doctor finishing work before the scheduled time, with another doctor available to take his place, and with them alternating?

The physician is an employee considered a special agent (ajir khass), and his time during work hours is owned by his employer. He is not permitted to delegate someone else in his place without the employer's permission. He must adhere to the terms of the agreed-upon contract, based on the Almighty's saying: "O YOU WHO HAVE BELIEVED, FULFILL [ALL] CONTRACTS." Any action that violates the contract, such as leaving before the end of working hours or appointing a substitute, is not permissible without permission.