Sahih al-Bukhari 4704
صحيح البخاري#4704Sahihحَدَّثَنَا آدَمُ، حَدَّثَنَا ابْنُ أَبِي ذِئْبٍ، حَدَّثَنَا سَعِيدٌ الْمَقْبُرِيُّ، عَنْ أَبِي هُرَيْرَةَ ـ رضى الله عنه ـ قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " أُمُّ الْقُرْآنِ هِيَ السَّبْعُ الْمَثَانِي وَالْقُرْآنُ الْعَظِيمُ ".
Narrated Abu Huraira:Allah's Messenger (ﷺ) said, "The Um (substance) of the Qur'an is the seven oft-repeated verses (Al-Mathani) and is the Great Qur'an (i.e. Surat-al-Fatiha)
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 65:226