Is a man sinful if he curses someone to himself without the curse reaching the one cursed or anyone else, with the cursing repeated due to a worldly situation that led to the curser's hatred of the one cursed?

We hope that there is no sin in a person cursing another person with something they did not say, or in front of people, because it falls under the general category of obsessive whispers (waswasah) which Allah pardons as long as they are not acted upon or spoken. A Muslim should strive to cultivate forgiveness, forbearance, and patience, especially in worldly matters, and should frequently supplicate: "Our Lord, do not put any rancor in our hearts toward those who have believed."