Musnad Ahmad 1153:1629

Muhammad ibn Bakr narrated to us, he said: Ibn Jurayj informed us, he said: ‘Ata’ informed me, from ‘Urwah ibn al-Zubayr, that he informed him, that ‘Aishah informed him, she said: The Prophet, peace and blessings of Allah be upon him, used to pray while I was lying across on the bed between him and the Qiblah. I said: "Is it between them the walls of the mosque?" She said: "No, in the house, towards its walls."