Musnad Ahmad 1153:398

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 Aisha, who said: "The Messenger of Allah, peace and blessings of Allah be upon him, used to remember Allah, the Almighty and Majestic, at all of his times."