What should a person do who commits many sins and transgressions, repents then relapses, maintains his prayers in the mosque, and suffers from disbelief-inducing whispers and negative thoughts? And is there any repentance for him?

The door of repentance is open for the Muslim until the sun rises from the west or the soul reaches the throat. This person must repent sincerely before death, and turn away from the whispers of Satan and not pay attention to them, because whispers do not affect faith. He should stay away from thinking about these matters and from isolation, and occupy his time with what benefits him and his nation, such as learning, working, exercising, and beneficial stories, and he should frequently remember Allah and observe the prescribed morning and evening remembrances.