Mishkat al-Masabih 4 Prayer كتاب الصلاة 470

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

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.)