It is narrated from Sayyidah Aishah (may Allah be pleased with her): None of us had more than one garment, and she would menstruate in it. If any of the blood got on the garment, she would moisten it with her saliva and then scrape it off with her nail.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4097