Abu Dawud
Purification (Kitab Al-Taharah)
Book Number: 001 / Hadith Number: 305
Narated By Umm Habibah daughter of Jahsh : Ikrimah said: Umm Habibah daughter of Jahsh had a prolonged flow of blood. The Prophet (pbuh) commanded her to refrain (from prayer) during her menstrual period; then she should wash and pray, if she sees anything (which renders ablution void) she should perform ablution and pray.