Is it Islamically permissible for the children of a woman who donated her inheritance share for the construction of a mosque to cancel an exchange deal their mother made with another heir for the purpose of completing the mosque's construction, on the grounds that the deal was unfair to their mother, knowing that the mosque has already been built and the other heir cannot reclaim his share?

If a woman relinquishes her land to a relative in exchange for his land for the purpose of building a mosque, her action is legitimate and her contract is valid. The heirs are not permitted to nullify the contract, and the relative has the right to take them to court. The children must fear Allah and cease their mistreatment of their mother after her death. If the brother relinquishes his right willingly, he will be rewarded.