The Prophet ﷺ passed by him when he was praying, and called him. He said: "I finished praying, then I came to him, and he said: 'What kept you from answering me?' He said: 'I was praying.' He said: 'Does not Allah say: O you who believe! Answer Allah (by obeying Him) and (His) Messenger when he calls you to that which will give you life? Shall I not teach you the greatest surah before I leave the masjid?' Then he went to leave, and I said: 'O Messenger of Allah, what about what you said?' He said: "All praise and thanks be to Allah, Lord of all that exists. These are the seven oft-recited that I have been given, and the Grand Quran.'"  

أَنَّ النَّبِيَّ ﷺ مَرَّ بِهِ وَهُوَ يُصَلِّي فَدَعَاهُ قَالَ فَصَلَّيْتُ ثُمَّ أَتَيْتُهُ فَقَالَ مَا مَنَعَكَ أَنْ تُجِيبَنِي قَالَ كُنْتُ أُصَلِّي قَالَ أَلَمْ يَقُلِ اللَّهُ ﷻ { يَا أَيُّهَا الَّذِينَ آمَنُوا اسْتَجِيبُوا لِلَّهِ وَلِلرَّسُولِ إِذَا دَعَاكُمْ لِمَا يُحْيِيكُمْ } أَلاَ أُعَلِّمُكَ أَعْظَمَ سُورَةٍ قَبْلَ أَنْ أَخْرُجَ مِنَ الْمَسْجِدِ قَالَ فَذَهَبَ لِيَخْرُجَ قُلْتُ يَا رَسُولَ اللَّهِ قَوْلَكَ قَالَ الْحَمْدُ لِلَّهِ رَبِّ الْعَالَمِينَ هِيَ السَّبْعُ الْمَثَانِي الَّذِي أُوتِيتُ وَالْقُرْآنُ الْعَظِيمُ  

"The Messenger of Allah ﷺ said: 'Allah, the Mighty and Sublime, did not reveal in the Tawrah or the Injil anything like Umm Al-Quran (Al-Fatihah), which is the seven oft-recited, and (Allah said) it is divided between Myself and My slave will have what he asked for.'"  

قَالَ رَسُولُ اللَّهِ ﷺ مَا أَنْزَلَ اللَّهُ ﷻ فِي التَّوْرَاةِ وَلاَ فِي الإِنْجِيلِ مِثْلَ أُمِّ الْقُرْآنِ وَهِيَ السَّبْعُ الْمَثَانِي وَهِيَ مَقْسُومَةٌ بَيْنِي وَبَيْنَ عَبْدِي وَلِعَبْدِي مَا سَأَلَ  

"The Prophet ﷺ was given seven oft-recited; the seven long ones."  

أُوتِيَ النَّبِيُّ ﷺ سَبْعًا مِنَ الْمَثَانِي السَّبْعَ الطُّوَلَ  

Concerning the words of Allah, the Mighty and Sublime: "Seven of Al-Mathani (seven repeatedly-recited): "The seven long ones."  

فِي قَوْلِهِ ﷻ { سَبْعًا مِنَ الْمَثَانِي } قَالَ السَّبْعُ الطُّوَلُ