Hadithcore
Mishkat al-Masabih, 1052

Ibn ‘Umar reported God’s Messenger as saying, “Prayer said in a congregation is twenty-seven degrees more excellent than prayer said by a single person.” (Bukhari and Muslim.)

عَنِ ابْنِ عُمَرَ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «صَلَاةُ الْجَمَاعَةِ تَفْضُلُ صَلَاة الْفَذ بِسبع وَعشْرين دَرَجَة»

References1 variant
In-Book Reference
Book 4, Hadith 470