Musnad Ahmad 30:3711

Rawh narrated to us, Ibn Jurayj narrated to us, 'Umar ibn 'Ata' ibn Abi al-Khuwar informed me that while he was sitting with Nafi' ibn Jubayr, Abu 'Abd Allah, the son-in-law of Zayd ibn Zabban al-Juhani, passed by them. Nafi' called him and said: I heard Abu Hurayrah say: The Messenger of Allah (peace and blessings of Allah be upon him) said: "A prayer with the Imam is better than twenty-five prayers that one prays alone."