Sahih Muslim 8649
In-book no 1372حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، قَالَ قَرَأْتُ عَلَى مَالِكٍ عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " صَلاَةُ الْجَمَاعَةِ أَفْضَلُ مِنْ صَلاَةِ الْفَذِّ بِسَبْعٍ وَعِشْرِينَ دَرَجَةً " .
Ibn Umar reported Allah's Messenger (ﷺ) assaying: Prayer said in a congregation is twenty-seven degrees more excellent than prayer said by a single person.