Question: Someone hired a person to wash his car every morning at a monthly fee. During the month the carowner left with his car before the worker came at 06:00 AM. The car was subsequently washed only once during the entire month, but the worker came to claim the full monthly fee.
Answer: This is a corrupt contract due to the high level of vagueness with regard to the service; a level of vagueness that leads to conflict between the parties. A time should have been specified either for the time the washing should start or end (not both, unless one wants to hire based on time rather than work accomplished.) Since the contract is corrupt, the owner of the car needs to compensate the worker hired for the one time he washed only. The compensation should be the going rate for this job in the market (i.e. for washing the car once - no consideration is given to the monthly fee agreed upon since the contract was corrupt). Both parties committed a sin.
When a hiring contract is corrupt, then the worker takes only the going rate of the market for the work he has done. However, this is only as long as this rate does not exceed the rate that was agreed upon for the work. If the going market rate exceeds the rate that was agreed upon in the contract, then the worker takes only the rate that was agreed upon. In the above case there was no stated rate for one day, but for a month as a whole only.