Musnad Ahmad 1153:1414

Bahz and Ibn Ja'far narrated to us, they said: Shu'bah narrated to us. Bahz said: Sa'd ibn Ibrahim informed me, he said: I heard 'Urwah ibn al-Zubayr narrating from 'Aishah: "That the Messenger of Allah (peace and blessings of Allah be upon him) used to pray while I was between him and the Qiblah." Ibn Ja'far said: Sa'd said: And I think he said: "And she was menstruating."