Abu Dawud Book 2, Hadith Number 1300.

Chapter : Abrogation of the prayer at night and convenience in it.

Narated By Ibn ‘Abbas : When the opening verses of Surah al-Muzzamil (lxxiii.) were revealed, the Companions would pray as long as they would pray during Ramadhan until its last verses were revealed. The period between the revelation of its opening and the last verses was one year.