Sahih Bukhari | Volume 1 | Hadith Number 324

Narrated by '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.