Musnad Ahmad 30:1891

Bahz narrated to us, Shu'bah narrated to us, Sa'd ibn Ibrahim narrated to us, from al-Agharr, from Abu Hurairah, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "A prayer in this mosque of mine is better than a thousand prayers in any other mosque, except for the Ka'bah."