What is obsessive-compulsive disorder, especially the obsession with water and impurity and the repetition of prayer, ablution, and verses, and what is its treatment?

Obsessive-compulsive disorder (OCD) is an illness that causes a person to repeatedly perform actions and entertain thoughts that are excessive. This can lead the patient to completely abandon work. Satan plays a significant role in instigating these obsessive whispers (waswas), and the illness may also have other psychological or educational factors. To overcome these obsessions, it is recommended to seek refuge in Allah through supplication (du'a), remembrance (dhikr), and seeking forgiveness (istighfar), as well as seeking refuge from Satan. The Messenger of Allah, peace and blessings be upon him, said: "That is a devil called Khanzab. If you sense him, seek refuge with Allah from him and spit three times to your left." Another part of the cure is to be mindful and attentive during an action and to ponder over it.