Musnad Ahmad 1153:541

Muhammad ibn Mus'ab narrated to us, he said: Al-Awza'i narrated to us, from Al-Zuhri, from 'Urwah, from 'Aishah, she said: "The Messenger of Allah, peace and blessings of Allah be upon him, would pray the 'Asr prayer while the sun was still shining in my chamber."