Musnad Ahmad 5:541

'Abdullah narrated to us, Yusuf al-Saffar, the freed slave of Banu Umayyah, and Sufyan ibn Waki' narrated to me, they said: Abu Bakr ibn 'Ayyash narrated to us, from Abu Ishaq, from Hubayrah ibn Yarim, from 'Ali, who said: "When the Messenger of Allah (peace and blessings of Allah be upon him) would enter the last ten [days of Ramadan], he would tighten his waist-wrapper and wake his wives." Ibn Waki' said: "He would lift his waist-wrapper."