The clarification that the Qur’an was revealed in seven ahruf (modes of recitation), and clarifying its meaning Sahih Muslim 819 a
وَحَدَّثَنِي حَرْمَلَةُ بْنُ يَحْيَى، أَخْبَرَنَا ابْنُ وَهْبٍ، أَخْبَرَنِي يُونُسُ، عَنِ ابْنِ شِهَابٍ، حَدَّثَنِي عُبَيْدُ اللَّهِ بْنُ عَبْدِ اللَّهِ بْنِ عُتْبَةَ، أَنَّ ابْنَ عَبَّاسٍ، حَدَّثَهُ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ "أَقْرَأَنِي جِبْرِيلُ - عَلَيْهِ السَّلاَمُ - عَلَى حَرْفٍ فَرَاجَعْتُهُ فَلَمْ أَزَلْ أَسْتَزِيدُهُ فَيَزِيدُنِي حَتَّى انْتَهَى إِلَى سَبْعَةِ أَحْرُفٍ " . قَالَ ابْنُ شِهَابٍ بَلَغَنِي أَنَّ تِلْكَ السَّبْعَةَ الأَحْرُفَ إِنَّمَا هِيَ فِي الأَمْرِ الَّذِي يَكُونُ وَاحِدًا لاَ يَخْتَلِفُ فِي حَلاَلٍ وَلاَ حَرَامٍ .
Translation
Ibn 'Abbas reported Allah's Messenger (ﷺ) as saying
Gabriel taught me to recite in one style. I replied to him and kept asking him to give more (styles), till he reached seven modes (of recitation). Ibn Shibab said: It has reached me that these seven styles are essentially one, not differing about what is permitted and what is forbidden.