صَحِيحُ مُسْلِمٍ
Sahih Muslim 650 b
The Book of Mosques and Places of Prayer
The virtue of prayer in congregation, and clarifying the stern warning against staying away from it, and that it is fard kifayah
وَحَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ، وَمُحَمَّدُ بْنُ الْمُثَنَّى، قَالاَ حَدَّثَنَا يَحْيَى، عَنْ عُبَيْدِ اللَّهِ، قَالَ أَخْبَرَنِي نَافِعٌ، عَنِ ابْنِ عُمَرَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ صَلاَةُ الرَّجُلِ فِي الْجَمَاعَةِ تَزِيدُ عَلَى صَلاَتِهِ وَحْدَهُ سَبْعًا وَعِشْرِينَ .
Ibn 'Umar reported Allah's Messenger (ﷺ) as saying: The prayer of a person in congregation is twenty-seven times in excess to the prayer said alone.
Sahih Muslim, 650 bSahihصحيح