Musnad Ahmad 27:933

Hassan narrated to us, Zuhair narrated to us, from Abu Ishaq, from al-Bahiy, from Ibn Umar, that the Prophet, peace and blessings of Allah be upon him, said to Aisha: "Hand me the prayer mat from the mosque." She said: "I am in a state of ritual impurity (hadath)." He said: "Is your menstruation in your hand?"