Muwatta Malik Book 8, Hadith 1
Yahya related to me from Malik from Nafi from Abdullah ibn Umar
that the Messenger of Allah, may Allah bless him and grant him peace,
said, "Prayer in congregation is better than the prayer of a man by
himself by twenty-seven degrees."
Yahya related to me from Malik from Abd ar-Rahman ibn al-Qasim that al-Qasim ibn Muhammad had done the same as Ibn Umar.
Yahya related to me from Malik from Ibn Shihab from Said ibn al- Musayyab from Abu Hurayra that the Messenger of Allah, may Allah bless him and grant him peace, said, "Prayer in congregation is better than the prayer of one of you on his own by twenty-five parts."