Is the husband's will not to marry after him binding? And is the wife deprived of his intercession if she marries his brother? And is it permissible for her to stipulate to him that she be a wife to her first husband in Paradise?

This will is not binding on the woman. Rather, she should marry to protect her chastity. Her condition that she be for her first husband in Paradise is meaningless, for it has been reported that she will be given a choice to be with the best of them in character, or she will be with her last husband. The wife of a martyr is among those who will receive his intercession, but there is no clear indication whether her second marriage deprives her of her martyr husband's intercession.