Abu Dawud Book 1, Hadith Number 269.
Chapter : A person who is sexually defiled is permitted to eat anything before washing.
Narated By ‘Aisha, Ummul Mu’minin : Khallas al-Hujari reported: ‘Aisha said: I and the Apostle of Allah (PBUH) used to pass night in one (piece of) cloth (on me) while I menstruated profusely. If anything from me (i.e. blood) smeared him (i.e. his body), he would wash that spot and would not exceed it (in washing), then he would offer prayer with it.