Hadith on Quran: Surat al-Fatihah is greatest chapter of Quran

Abu Sa’id ibn al-Mu’alla reported: I was praying in the mosque when the Messenger of Allah, peace and blessings be upon him, called out to me but I did not respond. I said later, “O Messenger of Allah, I was praying.” The Prophet said, “Did not Allah say: Respond to Allah and the Messenger when he calls you?” (8:24) Then, the Prophet said, “I will teach you the greatest chapter in the Quran before you leave the mosque.” The Prophet took me by the hand and when he intended to leave, I said to him, “Did you not say that you would teach me the greatest chapter in the Quran?” The Prophet said, “All praise is due to Allah, the Lord of the worlds (1:1), the seven oft-repeated verses and the great recitation given to me.”

Source: Ṣaḥīḥ al-Bukhārī 4720

Grade: Sahih (authentic) according to Al-Bukhari

عَنْ أَبِي سَعِيدِ بْنِ الْمُعَلَّى قَالَ كُنْتُ أُصَلِّي فَدَعَانِي النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَلَمْ أُجِبْهُ قُلْتُ يَا رَسُولَ اللَّهِ إِنِّي كُنْتُ أُصَلِّي قَالَ أَلَمْ يَقُلْ اللَّهُ  اسْتَجِيبُوا لِلَّهِ وَلِلرَّسُولِ إِذَا دَعَاكُمْ ثُمَّ قَالَ أَلَا أُعَلِّمُكَ أَعْظَمَ سُورَةٍ فِي الْقُرْآنِ قَبْلَ أَنْ تَخْرُجَ مِنْ الْمَسْجِدِ فَأَخَذَ بِيَدِي فَلَمَّا أَرَدْنَا أَنْ نَخْرُجَ قُلْتُ يَا رَسُولَ اللَّهِ إِنَّكَ قُلْتَ لَأُعَلِّمَنَّكَ أَعْظَمَ سُورَةٍ مِنْ الْقُرْآنِ قَالَ الْحَمْدُ لِلَّهِ رَبِّ الْعَالَمِينَ هِيَ السَّبْعُ الْمَثَانِي وَالْقُرْآنُ الْعَظِيمُ الَّذِي أُوتِيتُهُ

4720 صحيح البخاري كتاب فضائل القرآن باب فضل فاتحة الكتاب