Rabbits are normally very clean animals, and are constantly grooming themselves. Bathing a rabbit is usually highly discouraged by rabbit knowledgeable people, because it can be very dangerous to a rabbits health, as there is a risk of hypothermia if a rabbit isn't dried properly. And there is also the risk of some rabbits going into shock and dying from the stress of a bath. So it really is something to be strictly avoided except in very specific cases, and then needs to be handled with great care.
Usually the only reason any bathing at all needs to be considered is for extremely soiled bottoms that can't just be cleaned with a cloth(especially in warm climates where there is a risk of flystrike occurring because of wet soiled fur). In which case a limited 'butt bath' may be necessary along with thoroughly drying the bun. This type of problem most often only happens when a rabbit has health problems causing the dirty bum to occur. In which case a vet visit may also be needed.