Sahih Muslim Book 3, Hadith Number 625.

Chapter : The quantity of water that is desirable for a bath because of sexual intercourse, bathing of the male and female with one vessel in the same condition and washing of one of them with the left-over of the other.

‘Aisha reported: The Messenger of Allah (may peace be upon him) took a bath from the vessel (which contained seven to eight seers, i.e. fifteen to sixteen pounds) of water And I and he (the Holy Prophet) took a bath from the same vessel. And in the Hadith narrated by Sufyan the words are: “from one vessel”. Qutaiba said: Al-Faraq is three Sa’ (a cubic measuring of varying magnitude).