Musnad Ahmad 1153:1182

Khalaf ibn al-Walid narrated to us, Yahya ibn Zakariya ibn Abi Za'idah narrated to us, from his father, from Khalid ibn Salamah al-Makhzumi, from al-Bahiy, from 'Urwah, from 'Aishah, she said: "The Messenger of Allah, peace and blessings of Allah be upon him, used to remember Allah, the Mighty and Majestic, at all of his times."