The Prophet ﷺ said: "Ubayy, I was asked to recite the Qur'an and I was asked: 'In one mode or two modes?' The angel that accompanied me said: 'Say, in two modes', I said: 'In two modes', I was asked again: 'In two or three modes'. The matter reached up to seven modes. He then said: 'Each mode is sufficiently health-giving, whether you utter 'all-hearing and all-knowing' or instead 'all-powerful and all-wise'. This is valid until you finish the verse indicating punishment on mercy and finish the verse indicating mercy on punishment."  

قَالَ النَّبِيُّ ﷺ يَا أُبَىُّ إِنِّي أُقْرِئْتُ الْقُرْآنَ فَقِيلَ لِي عَلَى حَرْفٍ أَوْ حَرْفَيْنِ فَقَالَ الْمَلَكُ الَّذِي مَعِي قُلْ عَلَى حَرْفَيْنِ قُلْتُ عَلَى حَرْفَيْنِ فَقِيلَ لِي عَلَى حَرْفَيْنِ أَوْ ثَلاَثَةٍ فَقَالَ الْمَلَكُ الَّذِي مَعِي قُلْ عَلَى ثَلاَثَةٍ قُلْتُ عَلَى ثَلاَثَةٍ حَتَّى بَلَغَ سَبْعَةَ أَحْرُفٍ ثُمَّ قَالَ لَيْسَ مِنْهَا إِلاَّ شَافٍ كَافٍ إِنْ قُلْتَ سَمِيعًا عَلِيمًا عَزِيزًا حَكِيمًا مَا لَمْ تَخْتِمْ آيَةَ عَذَابٍ بِرَحْمَةٍ أَوْ آيَةَ رَحْمَةٍ بِعَذَابٍ  

[Machine] I read a verse and Ibn Mas'ud recited it differently, so I went to the Prophet ﷺ and said, "Didn't you recite to me the verse like this and that?" He replied, "Yes." Then Ibn Mas'ud said, "Didn't you recite it to me like this and that?" He replied, "Yes, both of you are correct, excellent in recitation." I then asked him to teach me the Quran and he struck my chest and said, "O Ubayy bin Ka'b, I was taught the Quran, and I recited it to you precisely." I said, "On two letters." He asked, "On two letters or three?" The angel with me said, "On three." So I said, "On three," until it reached seven letters, from which there is no other interpretation except for 'Shafin' and 'Kafin' if I say 'Ghafur-ur-Rahim' or 'Samī`an `Alīman' or 'Alīman Samī`an'. Thus, Allah will continue to do so unless you end a verse of punishment with mercy or a verse of mercy with punishment.  

قَرَأْتُ آيَةً وَقَرَأَ ابْنُ مَسْعُودٍ خِلَافَهَا فَأَتَيْتُ النَّبِيَّ ﷺ فَقُلْتُ أَلَمْ تُقْرِئْنِي آيَةَ كَذَا وَكَذَا؟ قَالَ بَلَى فَقَالَ ابْنُ مَسْعُودٍ أَلَمْ تُقْرِئْنِيهَا كَذَا وَكَذَا؟ فَقَالَ بَلَى كِلَاكُمَا مُحْسِنٌ مُجْمِلٌ قَالَ فَقُلْتُ لَهُ فَضَرَبَ صَدْرِي فَقَالَ يَا أُبَيُّ بْنَ كَعْبٍ إِنِّي أُقْرِئْتُ الْقُرْآنَ فَقُلْتُ عَلَى حَرْفَيْنِ فَقَالَ عَلَىحَرْفَيْنِ أَوْ ثَلَاثَةٍ؟ فَقَالَ الْمَلَكُ الَّذِي مَعِي عَلَى ثَلَاثَةٍ فَقُلْتُ عَلَى ثَلَاثَةٍ حَتَّى بَلَغَ سَبْعَةَ أَحْرُفٍ لَيْسَ مِنْهَا إِلَّا شَافٍ كَافٍ إِنْ قُلْتَ غَفُورًا رَحِيمًا أَوْ قُلْتَ سَمِيعًا عَلِيمًا أَوْ عَلِيمًا سَمِيعًا فَاللهُ كَذَلِكَ مَا لَمْ تَخْتِمْ آيَةَ عَذَابٍ بِرَحْمَةٍ أَوْ آيَةَ رَحْمَةٍ بِعَذَابٍ  

[Machine] I read a verse, and Ibn Mas'ud also read it differently. So we went to the Prophet ﷺ , and I said, "Didn't you read the verse like this and this?" He said, "Yes." Ibn Mas'ud said, "Didn't you read it like this and this?" He said, "Yes." The Prophet ﷺ said, "Both of you are correct and beautifiers." I said, "Neither of us is better or more beautiful." He then struck my chest and said, "O Abu Bakr, was I not taught the Quran? Was it taught to me on one letter or two letters?" Then the angel who was with him said, "It was taught to you on two letters." So I said, "On two letters." Then it was asked, "On two letters or three?" So the angel with him said to me, "On three." So I said, "On three." This continued until it reached seven letters. Then the angel said, "There is nothing in it except for a shad and a kaf." I said, "Forgiving, Merciful, All-Knowing, Forbearing, All-Hearing, All-Knowing, Mighty, Wise." Similar to this, unless a verse ends with punishment and mercy, or mercy and punishment. And Ma'mar narrated it from Qatadah, and he sent it.  

قَرَأْتُ آيَةً وَقَرَأَ ابْنُ مَسْعُودٍ قِرَاءَةً خِلَافَهَا فَأَتَيْنَا النَّبِيَّ ﷺ فَقُلْتُ أَلَمْ تُقْرِأْنِي آيَةَ كَذَا وَكَذَا؟ قَالَ بَلَى قَالَ ابْنُ مَسْعُودٍ أَلَمْ تُقْرِأْنِيهَا كَذَا وَكَذَا؟ قَالَ بَلَى قَالَ كِلَاكُمَا مُحْسِنٌ مُجْمِلٌ قُلْتُ مَا كِلَانَا أَحْسَنَ وَلَا أَجْمَلَ قَالَ فَضَرَبَ فِي صَدْرِي وَقَالَ يَا أُبَيُّ أُقْرِئْتُ الْقُرْآنَ فَقِيلَ لِي عَلَى حَرْفٍ أَمَ عَلَى حَرْفَيْنِ؟ فَقَالَ الْمَلَكُ الَّذِي مَعِي عَلَى حَرْفَيْنِ فَقُلْتُ عَلَى حَرْفَيْنِ فَقِيلَ لِي عَلَى حَرْفَيْنِ أَمْ ثَلَاثَةٍ؟ فَقَالَ لِيَ الْمَلَكُ الَّذِي مَعِي عَلَى ثَلَاثَةٍ فَقُلْتُ ثَلَاثَةٌ حَتَّى بَلَغَ سَبْعَةَ أَحْرُفٍ قَالَ لَيْسَ فِيهَا إِلَّا شَافٍ كَافٍ قُلْتُ غَفُورٌ رَحِيمٌ عَلَيْمٌ حَلِيمٌ سَمِيعٌ عَلِيمٌ عَزِيزٌ حَكِيمٌ نَحْوُ هَذَا مَا لَمْ يَخْتِمْ آيَةَ عَذَابٍ بِرَحْمَةٍ أَوْ رَحْمَةٍ بِعَذَابٍ وَرَوَاهُ مَعْمَرٌ عَنْ قَتَادَةَ فَأَرْسَلَهُ