Fiqh-us-Sunnah Volume 3, Zakaat and Fasting, Fiqh 3.133B.
Section : Fasting, striving to perform as many acts of worship as possible during the last ten days of Ramadan.
Al-Bukhari and Muslim record from ‘Aishah that during the last ten days of Ramadan, the Messenger of Allah would wake his wives up during the night and then remain apart from them (that is, being busy in acts of worship). A version in Muslim states: “He would strive [to do acts of worship] during the last ten days of Ramadan more than he would at any other time.” At-Tirmizhi also recorded this from ‘Ali.