It is preferred to use a small amount of water in wudu’ and ghusl. It is mentioned in Sahih Muslim that the Messenger of Allah used a mudd مدّ (about half a cup) of water for wudu’ and a sa^ صاع (about a pint) for ghusl. A mudd is the fill of a pair of average-sized hands cupped together. The sa^ is four mudds. It is also mentioned in Sahih Muslim that the Messenger of Allah used six (6) mudds (about 3 cups) of water for wudu’ and thirty (30) mudds (about one cup less than a gallon) for ghusl.