From the practice of the Prophet of Allah 
we learn that we should be efficient with water and should not waste water.
- Anas  said: "The Prophet  used to wash with a saa' to five amdaad, and would do ablution with a mudd (of water)"
[Agreed upon: 201 & 737]
A saa' is equivalent to four mudds.
A mudd is a handful using two hands cupped together, of an average-sized man.