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كتاب المناقب
61  
Virtues and Merits of the Prophet (pbuh) and his Companions
(3)
Chapter: The Qur'an was revealed in the language of Quraish
(3)
باب نَزَلَ الْقُرْآنُ بِلِسَانِ قُرَيْشٍ
Sahih al-Bukhari 3506

Narrated Anas:

`Uthman called Zaid bin Thabit, `Abdullah bin Az-Zubair, Sa`id bin Al-`As and `AbdurRahman bin Al-Harith bin Hisham, and then they wrote the manuscripts of the Holy Qur'an in the form of book in several copies. `Uthman said to the three Quraishi persons. " If you differ with Zaid bin Thabit on any point of the Qur'an, then write it in the language of Quraish, as the Qur'an was revealed in their language." So they acted accordingly. (Sa`id bin Thabit was an Ansari and not from Quraish ).

حَدَّثَنَا عَبْدُ الْعَزِيزِ بْنُ عَبْدِ اللَّهِ، حَدَّثَنَا إِبْرَاهِيمُ بْنُ سَعْدٍ، عَنِ ابْنِ شِهَابٍ، عَنْ أَنَسٍ، أَنَّ عُثْمَانَ، دَعَا زَيْدَ بْنَ ثَابِتٍ وَعَبْدَ اللَّهِ بْنَ الزُّبَيْرِ وَسَعِيدَ بْنَ الْعَاصِ وَعَبْدَ الرَّحْمَنِ بْنَ الْحَارِثِ بْنِ هِشَامٍ فَنَسَخُوهَا فِي الْمَصَاحِفِ، وَقَالَ عُثْمَانُ لِلرَّهْطِ الْقُرَشِيِّينَ الثَّلاَثَةِ إِذَا اخْتَلَفْتُمْ أَنْتُمْ وَزَيْدُ بْنُ ثَابِتٍ فِي شَىْءٍ مِنَ الْقُرْآنِ، فَاكْتُبُوهُ بِلِسَانِ قُرَيْشٍ، فَإِنَّمَا نَزَلَ بِلِسَانِهِمْ‏.‏ فَفَعَلُوا ذَلِكَ‏.‏
Reference : Sahih al-Bukhari 3506
In-book reference : Book 61, Hadith 16
USC-MSA web (English) reference : Vol. 4, Book 56, Hadith 709
  (deprecated numbering scheme)