Musnad Ahmad 1153:593

Qutaybah ibn Sa'id narrated to us, Ibn Lahi'ah narrated to us, from Yazid ibn Abi Habib, from Suwayd ibn Qays, from Ibn Qurayt al-Sadafi, who said: I said to 'Aishah, may Allah be pleased with her, "Did the Messenger of Allah, peace and blessings of Allah be upon him, lie with you while you were menstruating?" She said: "Yes, when I would fasten my lower garment tightly upon myself. We did not have at that time except one mattress. So when Allah, the Almighty and Majestic, provided me with another mattress, I would withdraw from the Messenger of Allah, peace and blessings of Allah be upon him."