Musannaf Ibn Abi Shayba 1:1009

Abu Bakr narrated to us, he said: Abu Khalid al-Ahmar narrated to us, from Hisham ibn Urwah, from Fatimah, from Asma, who said: The Prophet, peace and blessings of Allah be upon him, was asked about menstrual blood that is on a garment. He said: "Scrape it with water, wash it, and pray in it."