Sahih Muslim Book 3, Hadith Number 631.

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.

Ibn Abbas said: Maimuna (the wife of the Holy Prophet)reported to me that she and the Apostle of Allah (may peace be upon him) took a bath from one vessel.