Reference: Sharh ‘Umdatul-Fiqh – Tape 1, Question No.18
Question: I have a restaurant and have employed a worker. I agreed with him that he would work for five hours every day. [That said] however, if there are fewer customers [than expected on any particular day], is it permissible for me to ask the employee to leave early – before the [agreed] five hours – and only pay him for the hours he has worked?
Response: That is dependant upon what you have both agreed. If you have agreed upon this, then there is no harm [in asking the employee to leave early, because] the Muslims are bound by their agreements. If you have agreed on this, then there is no harm.