Musnad Ahmad 1168:3

Yahya ibn Sa'id narrated to us, from Sufyan, who said: Thabit Abu al-Miqdam narrated to me, who said: 'Adi ibn Dinar narrated to me, who said: I heard Umm Qays bint Mihsan say: I asked the Messenger of Allah, peace and blessings of Allah be upon him, about a garment that is stained with menstrual blood. He said: "Scrape it with a rib, and wash it with water and lotus leaves (sidr)."