Musnad Ahmad 1153:890

'Affan narrated to us, he said: Wuhayb narrated to us, he said: Mansur ibn 'Abd al-Rahman narrated to us, from his mother, from 'Aishah, that a woman came to the Prophet, peace and blessings of Allah be upon him, and said: "O Messenger of Allah, how do I perform ghusl when I become pure [from menses]?" He said: "Take a piece of cloth scented with musk, and purify yourself with it." She said: "How do I purify myself with it?" He said: "Purify yourself with it." She said: "How do I purify myself with it?" Then the Messenger of Allah, peace and blessings of Allah be upon him, glorified Allah [said SubhanAllah] and turned away from her, then said: "Purify yourself with it." 'Aishah said: I understood what the Messenger of Allah, peace and blessings of Allah be upon him, wanted, so I took her, pulled her toward me, and informed her of what the Messenger of Allah, peace and blessings of Allah be upon him, wanted.