What is the ruling on expiation in Islam for a person who caused a car accident that led to the death of four people, three of whom were accompanying the deceased driver, knowing that the deceased driver was the one who caused the accident? And is it permissible to adopt one of the madhhabs that permit not fasting as expiation?

If the driver of the other vehicle was the cause of the accident, and the person concerned was unable to avoid it, then there is no guarantee (daman) or expiation (kaffarah) upon him.

However, if he could have avoided the accident but failed to do so due to inattentiveness, this is considered accidental killing (qatl khata'), and two things are required: 1. Blood Money (Diyah): This is incumbent upon the 'aqilah (male relatives on the father's side) of the killer, and it may be distributed between the families of both drivers according to their percentage of involvement in the error. 2. Expiation (Kaffarah): This is the freeing of a slave, or fasting for two consecutive months for each deceased person. The expiation multiplies with the number of deceased.