Sahih Muslim Book 3, Hadith Number 629.

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: I and the Messenger (may peace be upon him) took a bath from the same vessel and our hands alternated into it in the state that we had had sexual intercourse.