Musnad Abu Ya'la al-Mawsili 154:157

Abu Khaythama narrated to us, Yazid bin Harun narrated to us, Abd al-Malik bin Abi Sulayman informed us, from Ata, from Ibn Umar, from the Prophet (peace and blessings of Allah be upon him), who said: "A prayer in this mosque of mine is better than a thousand prayers in what is other than it of the mosques, except the Sacred Mosque (al-Masjid al-Haram)."