Musnad Ahmad 1153:1934

'Abd al-Razzaq narrated to us, Ma'mar narrated to us, from al-Zuhri, from 'Urwah, from 'Aishah, that the Messenger of Allah (may Allah bless him and grant him peace) used to perform i'tikaf during the last ten days of Ramadan until Allah, the Mighty and Majestic, took his soul.