سُنَنُ النَّسَائِيِّ
Sunan an-Nasa’i 837
The Book of Leading the Prayer (Al-Imamah)
Virtue of (prayer in) congregation
أَخْبَرَنَا قُتَيْبَةُ، عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ صَلاَةُ الْجَمَاعَةِ تَفْضُلُ عَلَى صَلاَةِ الْفَذِّ بِسَبْعٍ وَعِشْرِينَ دَرَجَةً .
It was narrated from Ibn 'Umar that the Messenger of Allah (ﷺ) said: "Praying in congregation is twenty-seven times better than praying alone."
Sunan an-Nasa'i, 837Sahih (Darussalam)