Musnad Abu Ya'la al-Mawsili 150:373

Abdullah ibn Muhammad ibn Asma’ narrated to us, Mahdi narrated to us, Hisham ibn Urwah narrated to us, from his father, from Aisha, that she was asked about the prayer of the Prophet (may Allah bless him and grant him peace). She said: "He used to pray while sitting. When he wanted to bow, he would stand and recite thirty or forty verses, then he would bow and prostrate."