The Messenger of Allah ﷺ said, "A prayer in this mosque of mine is better than a thousand prayers in any other mosque, except for the Kaabah."
حدثنا بهز حدثنا شعبة قال حدثني سعد بن إبراهيم عن الأغر
أن رسول الله ﷺ قال صلاة في مسجدي هذا أفضل من ألف صلاة فيما سواه من المساجد إلا الكعبة
Its isnad is sahih, it appeared previously at 1605, Nasai narrated it 5/213 no. 2998 in the chapters on Rites of Pilgrimage, on the merit of prayer in Masjid al-Haram, and similarly Bukhari 2/76 on the merit of prayer in the masjid of Makkah, and Muslim 2/1012 no. 1394.