Mishkat al-Masabih 752

Anas b. Malik reported God’s Messenger as saying, “A man’s prayer in his house is equivalent to a single observance of prayer, his prayer in a tribal mosque is equivalent to twenty-five, his prayer in a mosque in which the Friday prayer is observed is equivalent to five hundred, his prayer in the Aqsa mosque is equivalent to fifty thousand, his prayer in my mosque is equivalent to fifty thousand, and his prayer in the sacred mosque (the Ka’ba) is equivalent to a hundred thousand.” Ibn Majah transmitted it.