It is narrated from Sayyidah Asma bint Abi Bakr (may Allah be pleased with her) that she asked the Prophet (peace and blessings be upon him) about menstrual blood that gets on a garment, and he (peace and blessings be upon him) said: "Scrape it off, then rub it with water, then sprinkle it."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20658