Does a servant's forgiveness of someone who committed a grave sin against him necessitate Allah Almighty's forgiveness for the sinner, even if he died persisting in his sin without repentance?

Sins related to human beings, such as disobedience to parents, backbiting, and slander, are not expiated merely by the forgiveness of the wronged party. Rather, repentance to Allah the Almighty is necessary, because these sins combine the right of Allah with the right of the servant.

Al-Nawawi, may Allah have mercy on him, said: "If the sin relates to a human being, its conditions are four: to cease the sin, to regret having committed it, to resolve never to return to it, and to free oneself from the right of its owner."

Ibn al-Qayyim, may Allah have mercy on him, said: "Because in this offense there are two rights: a right of Allah and a right of the human being. So, repentance from it is by seeking release from the human being for his right, and regret between oneself and Allah for His right."