Musnad Ahmad 5:540

Abdullah narrated to us, Abu Khaythama narrated to me, Abd al-Rahman ibn Mahdi narrated to us, from Sufyan, and Shu'bah, and Isra'il, from Abu Ishaq, from Hubayrah, from Ali: "That the Prophet, peace and blessings of Allah be upon him, used to wake his family during the last ten nights of Ramadan."