What is the ruling on someone who caused a man's death in a car accident, then left him in the hospital, which led to his death due to neglect, even though the deceased's family forgave him? And what is the expiation for that?

If a man dies in a car accident and the driver is at fault, it is considered an accidental killing, and thus requires the payment of blood money (diyya) and expiation (kaffarah). If the family of the deceased pardons the blood money, it is waived, but the expiation remains, which is fasting for two consecutive months. Feeding the poor is not permissible as a substitute for this expiation, as it is not mentioned in the religious text.