Abu Dawud Book 1, Hadith Number 363.

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

Narated By Umm Qays daughter of Mihsan : I asked the Prophet (PBUH) about the blood of menstruation on the clothe. He said: Erase it off with a piece of wood and then wash it away with water and the leaves of the lote-tree.