From Sahih Bukhari (Hadith 648):
Narrated Abu Salama bin `Abdur Rahman:Abu Huraira said, "I heard Allah's Messenger (ﷺ) saying, 'The reward of a prayer in congregation is twenty five times greater than that of a prayer offered by a person alone. The angels of the night and the angels of the day gather at the time of Fajr prayer.' " Abu Huraira then added, "Recite the Holy Book if you wish, for "Indeed, the recitation of the Qur'an in the early dawn (Fajr prayer) is ever witnessed." (17:)
Reference: Bukhari 648