Musnad Abu Ya'la al-Mawsili 150:229

'Abd al-A'la narrated to us, Sufyan ibn 'Uyaynah narrated to us, from Mansur, from his mother, from 'A'ishah, that a woman asked the Prophet, peace and blessings of Allah be upon him, about her ritual bath (ghusl) from menstruation. He instructed her on how to perform the ritual bath, then said: "Take a piece of cotton scented with musk and purify yourself with it." She said: "How do I purify myself with it?" He covered his face with the edge of his garment and said: "Subhan Allah (Glory be to Allah), purify yourself with it." 'A'ishah said: "I pulled the woman toward me and said: 'Follow the traces of blood with it.'"