Sahih al-Bukhari 4984
صحيح البخاري#4984SahihNarrated 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
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 66:6