What is the ruling on the obsessive-compulsive disorder that afflicts my cousin, making him exaggerate in bathing and ablution, believe that everything he touches is impure, discard his clothes after each time he wears them, and constantly think about impurity, which has caused him problems with his family?

A young person must understand that obsessive doubt (waswasah) is a dangerous disease that corrupts both religious practice and worldly life. They must strive against it and get rid of it by all means. If they perform ghusl (ritual bath), they should not repeat it. Rather, they should wash their body until they are certain that the water has covered all parts of it. They should ignore the whispers of Satan suggesting that some part of their body was not reached by the water. If Satan whispers to them about something being impure, they should remember that the default state is purity, and impurity is only judged with certainty. They should apply this principle to all forms of obsessive doubt.