It was narrated that Abu Sa'eed bin Mu'alla said:
"The Messenger of Allahﷺ said to me: 'Shall I not teach you the greatest Surah in the Quran before I leave the masjid?' Then the Propehtﷺ went to leave, so I reminded him, and he said: Al-hamdulillahi Rabbil-Alameen (All the praise is to Allah, the Lord of all that exists). It is the Seven Oft-Recited Verses, and it is the Grand Quran that has been given to me.'"

حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا غُنْدَرٌ، عَنْ شُعْبَةَ، عَنْ خُبَيْبِ بْنِ عَبْدِ الرَّحْمَنِ، عَنْ حَفْصِ بْنِ عَاصِمٍ، عَنْ أَبِي سَعِيدِ بْنِ الْمُعَلَّى، قَالَ قَالَ لِي رَسُولُ اللَّهِ ﷺ " أَلاَ أُعَلِّمُكَ أَعْظَمَ سُورَةٍ فِي الْقُرْآنِ قَبْلَ أَنْ أَخْرُجَ مِنَ الْمَسْجِدِ " . قَالَ فَذَهَبَ النَّبِيُّ ﷺ لِيَخْرُجَ فَأَذْكَرْتُهُ فَقَالَ " { الْحَمْدُ لِلَّهِ رَبِّ الْعَالَمِينَ} وَهِيَ السَّبْعُ الْمَثَانِي وَالْقُرْآنُ الْعَظِيمُ الَّذِي أُوتِيتُهُ " .