Should the money given by the grandmother to the father before her death—on condition that he help her with medication and doctors—be deducted from the inheritance?

If a mother pays her son money for her service in taking her to the doctor and buying medicine, then this contract is void because the benefit is neither known nor precisely defined. Scholars have differed on the validity of a parent hiring their child. The Hanafis hold that it is not valid if the service is obligatory upon the child, while the Shafi'is and Hanbalis consider it valid. According to the view that the hiring is void, the son must return the money to his mother's estate, and he may deduct transportation and medicine expenses if he did not provide them gratuitously.