Sahih Muslim 650
Sahih Muslim · Book 5: 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
وَحَدَّثَنَاهُ ابْنُ رَافِعٍ ، أَخْبَرَنَا ابْنُ أَبِي فُدَيْكٍ ، أَخْبَرَنَا الضَّحَّاكُ ، عَنْ نَافِعٍ ، عَنِ ابْنِ عُمَرَ ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " بِضْعًا وَعِشْرِينَ " .
Ibn 'Umar reported from the Messenger of Allah (ﷺ) as some and twenty (degrees).