Abu Dawud Book 1, Hadith Number 305.

Chapter : A person who is sexually defiled is permitted to eat anything before washing.

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.