Musnad Ahmad 27:909

Musa ibn Dawud narrated to us, Abdullah ibn Umar narrated to us, from Nafi’, from Ibn Umar, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "A prayer in my mosque is better than a thousand prayers in any other, except for the Sacred Mosque (al-Masjid al-Haram)."