Musnad Ahmad 1153:1255

'Abd al-Samad narrated to us, Hammam narrated to us, he said: 'Ali ibn Zayd narrated to me, he said: Umm Muhammad narrated to me, that 'Aishah narrated to her: "That the Messenger of Allah, peace and blessings of Allah be upon him, would not sleep, neither by night nor by day, and then wake up, except that he would use the siwak before performing wudu."