It was narrated that Ibn 'Umar said:
"The Messenger of Allah said: 'The prayer of a man in congregation is twenty-seven levels more virtuous than a man's prayer on his own.'"

حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ عُمَرَ، رُسْتَهْ حَدَّثَنَا يَحْيَى بْنُ سَعِيدٍ، حَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ عُمَرَ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ قَالَ رَسُولُ اللَّهِ ﷺ " صَلاَةُ الرَّجُلِ فِي جَمَاعَةٍ تَفْضُلُ عَلَى صَلاَةِ الرَّجُلِ وَحْدَهُ بِسَبْعٍ وَعِشْرِينَ دَرَجَةً " .