Abu Dawud Book 1, Hadith Number 365.
Chapter : A peerson who is sexually defiled is permitted to eat anything before washing.
Narated By Abu Hurairah : Khawlah, daughter of Yasar came to the Prophet (PBUH) and said: Apostle of Allah, I have only one clothe and I menstruate in it, how should I do? He said: When you are purified, wash it and pray in it. She asked: If the blood is not removed, (then what)? He said: It is enough for you to wash the blood, its mark will not do any harm to you.