Bukhari

Hadith Commentary:
What happened was that the Qur’an had been compiled during the caliphate of Abu Bakr as-Siddiq radi Allahu anhu with the consensus of all the Companions. That same Qur’an remained with Umar radi Allahu anhu during his caliphate, and after the death of Umar radi Allahu anhu, it was with Umm al-Mu’minin Hafsah radi Allahu anha.
Uthman radi Allahu anhu had that very Qur’an brought from Hafsah radi Allahu anha and had its copies written by the aforementioned people, and then sent one copy each to Iraq, Egypt, Sham (Greater Syria), Iran, and other lands.
The reason Uthman radi Allahu anhu is called “Jami‘ al-Qur’an” (the one who gathered the Qur’an) is precisely because he had copies of the Qur’an written in clear scripts and sent to various lands. It is not that the Qur’an was compiled during his time; rather, the Qur’an had already been compiled during the time of the Prophet sallallahu alayhi wa sallam, and whatever remained scattered was all gathered in one place during the caliphate of Abu Bakr as-Siddiq radi Allahu anhu.
Here, the purpose of the chapter is to mention the virtue of the Quraysh, that the Noble Qur’an was revealed according to their dialect.

Hadith Commentary:
➊
The Messenger of Allah (sallallahu alayhi wa sallam) himself was a Qurayshi, and the Noble Qur’an was revealed to him in accordance with this mother tongue so that he could first understand it thoroughly himself, and then explain it to others in the best manner.

➋
Before the transcription commissioned by Uthman (radi Allahu anhu), the Noble Qur’an was already present in written form, and a copy of it was in the possession of Hafsa (radi Allahu anha). Uthman (radi Allahu anhu) sent her a message requesting that she send the Qur’anic manuscripts she had, promising to return them after the new codices were prepared. Accordingly, Uthman (radi Allahu anhu) had copies of the Noble Qur’an prepared and sent them to the various regions of the world.

He instructed that the Qur’an be written, and said: If you disagree about anything concerning the orthography of the Qur’an, then write it according to the dialect of Quraysh. Thus, there was a disagreement regarding the word “tabut.” Zayd (radi Allahu anhu) wanted to write it as “tabuwah,” whereas among the Quraysh its orthography was “tabut,” so it was written according to their dialect.

➌
Imam Bukhari (rahimahullah) has established the virtue of Quraysh from this hadith. He has also given a similar heading to this hadith in the Book of the Virtues of the Qur’an: The Qur’an was revealed according to the dialect of Quraysh and the Arabs. (: Fath al-Bari: 6/659)

After the codices were written, Hafsa’s (radi Allahu anha) manuscript was returned to her, and the remaining personal manuscripts were burned. (: Umdat al-Qari: 11/257)