Maliks Muwatta Book 8, Hadith Number 2.
Section : The Superiority of Prayer in Congregation over Prayer Done Alone.
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.”