Sahih Bukhari Volume 003, Book 031, Hadith Number 151.
Narated By Zainab : (Daughter of Um Salama) that her mother said, "While I was (lying) with Allah's Apostle underneath a woolen sheet, I got the menstruation, and then slipped away and put on the clothes (which I used to wear) in menses. He asked, "What is the matter? Did you get your menses?" I replied in the affirmative and then entered underneath that woolen sheet. I and Allah's Apostle used to take a bath from one water pot and he used to kiss me while he was fasting."