What is the cure for obsessive-compulsive disorder (waswas), especially during obligatory fasting, and what is its effect on prayer locations and the time spent in purification and prayer, and why does it disappear during voluntary fasting?

The treatment for obsessive thoughts (waswas) is to ignore them and pay them no mind, whether they concern fasting, istinja (definition) (cleaning oneself after relieving oneself), wudu (ablution), prayer, or anything else. The person afflicted with waswas must strive against these whispers and not give them any attention. If Satan whispers to him about an obligatory fast, purity, or anything else, he should cast these whispers aside. He should purify himself in a normal manner without over-exertion, and he should not exceed the prescribed amount when washing his limbs. He should pray in any place unless he is certain of its impurity. By doing so, the waswas will be repelled, by the will of Allah.