حَدَّثَنَا 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 (PBUH) assaying: Prayer said in a congregation is twenty-seven degrees more excellent than prayer said by a single person. Translation Not Available

Book Ref: Sahih Muslim Book 5 Hadith 1365
Web Ref:  Sahih Muslim Book 4 Hadith 650 a