Sahih Muslim Book 3, Hadith Number 626.

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.

Abu Salaman. ‘Abd al-Rahman reported: I along with the foster brother of ‘Aisha went to her and he asked about the bath of the Apostle (may peace be upon him) because of sexual intercourse. She called for a vessel equal to a Sa’ and she took a bath and there was a curtain between us and her. She poured water on her head thrice and he (Abu Salama) said: The wives of the Apostle (may peace be upon him) collected hair on their heads and these lopped up to ears(and did not go beyond that).