Narrated Anas bin Malik:
(The Caliph `Uthman ordered Zaid bin Thabit, Sa`id bin Al-As, `Abdullah bin Az-Zubair and `Abdur- Rahman bin Al-Harith bin Hisham to write the Qur'an in the form of a book (Mushafs) and said to them. "In case you disagree with Zaid bin Thabit (Al-Ansari) regarding any dialectic Arabic utterance of the Qur'an, then write it in the dialect of Quraish, for the Qur'an was revealed in this dialect." So they did it.
Reference | : Sahih al-Bukhari 4984 |
In-book reference | : Book 66, Hadith 6 |
USC-MSA web (English) reference | : Vol. 6, Book 61, Hadith 507 |
(deprecated numbering scheme) |