وَعَنِ ابْنِ عَبَّاسٍ رَضِيَ اللَّهُ عَنْهُمَا
قَالَ: إِنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «أَقْرَأَنِي جِبْرِيل على حرف فَرَاجعه فَلم أزل استزيده ويزيدني حَتَّى انْتهى إِلَى سَبْعَةِ أَحْرُفٍ». قَالَ ابْنُ شِهَابٍ: بَلَغَنِي أَنَّ تِلْكَ السَّبْعَةَ الْأَحْرُفَ إِنَّمَا هِيَ فِي الْأَمْرِ تَكُونُ وَاحِدًا لَا تَخْتَلِفُ فِي حَلَالٍ وَلَا حرَام
Ibn Abbas reported God’s messenger as saying, “Gabriel taught me to recite in one mode, and when I replied to him and kept asking him to give me more he did so till he reached seven modes.” Ibn Shihab said he had heard that those seven modes are essentially one, not differing about what is permitted and what is prohibited. (Bukhari and Muslim.)
Mishkat al-Masabih 2118, Book 9, The Excellent Qualities of the Qur'an, Hadith 104. 1 min read