It is narrated from Sayyidah Asma (may Allah be pleased with her) that a woman came to the Prophet (peace and blessings be upon him) and asked: If menstrual blood gets on the garment of one of us, what should she do? He (peace and blessings be upon him) said: "She should scrape it and then wash it, then sprinkle water on it and pray in it."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4105