Musnad Ahmad 26:773

Abu Dawud and ‘Affan narrated to us, they said: Hammam narrated to us, from Qatadah, from Muwarriq al-‘Ijli, from Abu al-Ahwas, from ‘Abdullah, from the Prophet, peace and blessings of Allah be upon him, who said: "The prayer of the congregation is superior to the prayer of a man alone by twenty-five prayers, all of them like his prayer." ‘Affan said: It reached me that Abu al-‘Awwam agreed with him.