The reward of the congregational prayer is twenty seven times greater (than that of the prayer offered by a person alone).
Sahih al-Bukhari Book 10, Hadith 46
← Previous Hadith 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 Quran in the early dawn (Fajr prayer) is ever witnessed." (17:78).

Sahih al-Bukhari Book 10, Hadith 45 Next Hadith → I heard Um Ad-Darda' saying, "Abu Ad-Darda' entered the house in an angry mood. I said to him. 'What makes you angry?' He replied, 'By Allah! I do not find the followers of Muhammad doing those good things (which they used to do before) except the offering of congregational prayer." (This happened in the last days of Abu Ad-Darda' during the rule of `Uthman) .

Sahih al-Bukhari Book 10, Hadith 47