It is narrated from Sayyidah Asma' (may Allah be pleased with her) that a woman asked the Messenger of Allah (peace and blessings be upon him) about menstrual blood that gets on clothing, and he (peace and blessings be upon him) said: "Scrape it, then rub it with water, then sprinkle it, and pray in it."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1157