What is the ruling on one who experiences frequent doubt in prayer and repeatedly pauses to determine which prayer he is in?

One who experiences frequent doubt in prayer, to the extent that it becomes a whisper (waswas), should not pay attention to their doubt or try to rectify it. Rather, they should complete their prayer and prostrate after the salutation (taslim) to spite Satan. They are not commanded to rectify it due to the hardship involved.