Bulugh al-Maram 779
Ibn Az-Zubair (RAA) narrated that the Messenger of Allah (ﷺ) said:
"Offering prayer in my mosque (in Madinah) is better than one thousand prayers elsewhere, save for those offered prayer in al-Masjid al-Haram (in Makkah). And prayer offered in al-Masjid al-Haram is better than prayer offered in my mosque by one hundred prayers." Related by Ahmad and Ibn Hibban graded it as Sahih.
وَعَنِ اِبْنِ اَلزُّبَيْرِ رَضِيَ اَللَّهُ عَنْهُمَا قَالَ: قَالَ رَسُولُ اَللَّهِ ‏- صلى الله عليه وسلم ‏-{ صَلَاةٌ فِي مَسْجِدِي هَذَا أَفْضَلُ مِنْ أَلْفِ صَلَاةٍ فِيمَا سِوَاهُ إِلَّا اَلْمَسْجِدَ اَلْحَرَامَ , وَصَلَاةٌ فِي اَلْمَسْجِدِ اَلْحَرَامِ أَفْضَلُ مِنْ صَلَاةٍ فِي مَسْجِدِي بِمِائَةِ صَلَاةٍ }  رَوَاهُ أَحْمَدُ, وَصَحَّحَهُ اِبْنُ حِبَّانَ  1‏ .‏‏1 ‏- صحيح.‏ رواه أحمد ( 4 / 5 )‏، وابن حبان ( 1620 )‏.‏