It was narrated that Asma' bint Abi Bakr said:
"The Messenger of Allah was asked about menstrual blood that gets on clothing. He said: 'Rub it off, wash it and perform prayer in (the garment).'" (DE)
English reference (DE): Vol. 1, Book 1, Hadith 629 (DE)
Arabic reference (DE): Book 1, Hadith 672 (DE)