Abu Dawud
Purification (Kitab Al-Taharah)
Book Number: 001 / Hadith Number: 81
Narated By Humayd al-Himyari : Humayd al-Himyari reported: I met a person (among the Companion of Prophet) who remained in the company of the Prophet (pbuh)for four years as AbuHurayrah remained in his company. He reported: The Apostle of Allah (pbuh) forbade that the female should wash with the water left over by the male, and that the male should wash with the left-over of the female.
The version of Musaddad adds: "That they both take the handful of water together."