What is the ruling on seeing the Prophet, peace and blessings be upon him, in a dream commanding one to perform ablution once, while suffering from obsessive thoughts regarding purification and prayer? And what is the ruling on working as a network engineer for companies that build communications for usurious banks and others?

The cure for obsessive-compulsive disorder (waswasah) is to ignore it and not pay attention to it. It is permissible to perform ablution (wudu') once or twice, and the Sunnah (definition) is three times, and it is not permissible to exceed three washes. Dreams that contradict the Sharia (definition) have no validity. Do not repeat ablution merely due to doubt or for the sake of waswasah. As for the work mentioned, it is not permissible to assist in sin and transgression. If a person knows that the networks are being established for an interest-based (ribawi) bank, then it is not permissible for him to work in their establishment.