Fiqh-us-Sunnah Volume 2, Supererogatory Prayer, Fiqh 2.020.
Section : The Late Night Prayer, tahajjud (qiyam al-Layil). Its excellence and merit from the Qur’an: Allah ordered his Messenger to perform salatul tahajjud: “And some part of the night awake for prayer, a largess for thee. It may be…