Musnad Ahmad 1168:6

Waki’ narrated to us, Isra’il narrated to us, from Thabit Abu al-Miqdam, from ‘Adi ibn Dinar, from Umm Qays bint Mihsan, she said: I asked the Messenger of Allah, peace and blessings of Allah be upon him, about menstrual blood that gets on a garment. He said: "Scrape it, even if with a rib."