Musnad Ahmad 1153:1127

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, from Ibrahim ibn al-Muhajir, who said: I heard Safiyyah narrating from ‘Aishah: That Asma’ asked the Prophet, peace and blessings of Allah be upon him, about the bath for menstruation. He said: "One of you takes her water and her lote-tree leaves and purifies herself, and performs the purification well. Then she pours [water] over her head and rubs it vigorously until it reaches the roots of her hair. Then she pours water over herself. Then she takes a piece of cloth scented with musk and purifies herself with it." Asma’ said: "And how does she purify herself with it?" He said: "Subhan Allah, purify yourself with it!" So ‘Aishah said, as if she were concealing that: "Follow the traces of the blood." And she asked him about the bath for major ritual impurity (janabah). He said: "You take water and purify yourself, and perform the purification well—or perform the purification thoroughly—then she pours [water] over her head and rubs it until it reaches the roots of her hair, then she pours water over herself." ‘Aishah then said: "Excellent are the women of the Ansar; shyness did not prevent them from seeking understanding in the religion."