Sahih al-Bukhari 4984
Book 66: Virtues of the Qur'an · Hadith 6
Hadith text
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
Anas bin Malik bataate hain: (Khalifa Uthman ne Zaid bin Thabit, Saeed bin Al-As, Abdullah bin Az-Zubair aur Abdur Rahman bin Al-Harith bin Hisham ko hukm diya ke wo Quran ko ek Kitaab (Mushaf) ki shakl mein likhein, aur unse kaha, 'Agar tum Zaid bin Thabit (Al-Ansari) se kisi Arabi lehje ke lafz ke baare mein ikhtelaf karo, to use Quraish ke lehje mein likho, kyunke Quran isi lehje mein naazil hua tha.' To unhone aisa hi kiya.)
Sahih al-Bukhari 4984 · Book 66, Hadith 6