What is the sufficient amount of water for ghusl from janabah, and is rubbing with the hand obligatory in it?

The Prophet, peace and blessings be upon him, used to perform ablution with one mudd (a measure) and perform ghusl (ritual bath) with one sa' (four mudds) up to five mudds. A mudd is equal to 0.688 liters, and a sa' is four mudds, so the sufficient amount for ghusl from janabah (ritual impurity) is 2.752 liters.