Sahih Bukhari
Menstrual Periods
Volume: 001 / Book Number: 006 / Hadith Number: 324
Narrated 'Aisha:
(the wife of the Prophet) Um Habiba got bleeding in between the periods for seven years. She asked Allah's Apostle about it. He ordered her to take a bath (after the termination of actual periods) and added that it was (from) a blood vessel. So she used to take a bath for every prayer.