Musnad Ahmad 30:494

'Abd al-Razzaq narrated to us, Ma'mar narrated to us, from al-Zuhri, from Abu Salamah, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The excellence of the prayer in congregation over the prayer of the individual is twenty-five [degrees]. The angels of the night and the angels of the day gather at the dawn prayer." He said: Then Abu Hurayrah would say: "And recite if you wish: {And [recite] the Qur'an of dawn. Indeed, the recitation of dawn is ever witnessed} [Al-Isra: 78]."