Musnad Ahmad 1153:1046

Waki' narrated to us, he said: Talhah ibn Yahya narrated to us, from Ubaydullah ibn Abdullah, he heard it from him, from Aisha: "That the Prophet, peace and blessings of Allah be upon him, prayed while he was wearing a *mirt* (a garment), part of which was upon her, and she was menstruating."