Bukhari

Hadith Commentary:
That is, in their respective places, only the arrangement of the surahs and the reasons for the recitation, etc., were altered by Uthman (radi Allahu anhu).
In the era of the Prophet (sallallahu alayhi wa sallam), this arrangement of the surahs did not exist, and for this reason, it is permissible for the one praying to recite whichever surah he wishes first and whichever he wishes afterwards; it is not obligatory to maintain their order.
However, it is more appropriate that in the first rak‘ah more verses are recited, and in the second rak‘ah a surah with fewer verses is recited.

Explanation:
Uthman al-Ghani (radi Allahu anhu) had many copies of the Noble Qur’an prepared, and after thorough examination, he distributed them throughout the Islamic state in such a manner that one copy was sent to Kufa, one to Basra, one to Sham (Greater Syria), and one was kept with himself in Madinah.
In some narrations, it is mentioned that seven codices were prepared, and one each was sent to Makkah, Sham, Yemen, Bahrain, Basra, and Kufa, and one was kept in Madinah.
This burning (of other copies) was entirely appropriate and dictated by wisdom.
This command was given by Uthman (radi Allahu anhu) in the presence of all the Companions.
They did not object to it.
Some have said that Uthman (radi Allahu anhu) gathered them and then had them burned.
From this hadith, it is also derived that it is permissible to burn those papers on which the name of Allah is written.
Now, the codex that was with Hafsah (radi Allahu anha) remained with her throughout her life.
When Marwan requested it, she did not give it; after her death, Marwan borrowed it from Abdullah ibn Umar (radi Allahu anhuma) and had it burned, so that no one had any other codex left.
However, it is said that Abdullah ibn Mas‘ud (radi Allahu anhu) did not give his copy even when Uthman (radi Allahu anhu) requested it.
But after the death of Abdullah ibn Mas‘ud (radi Allahu anhu), it is not known where that codex went.
In some narrations, it is mentioned that Ali (radi Allahu anhu) also prepared a codex in the order of revelation, but there is no information about that either.
Whatever Allah willed, that is what happened; only this ‘Uthmani codex remained in the world.
Whether in agreement or opposition, in every country and every sect, wherever you look, it is this very codex that is found.
(Wahidi)

Hadith Commentary:
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Hudhayfah radi Allahu anhu observed in the region of Azerbaijan that people were reciting the Qur’an in the languages of their various tribes and saying, “Our recitation is better than yours.”
In reality, the people of Sham would recite the Noble Qur’an according to the recitation of Ubayy ibn Ka‘b radi Allahu anhu, and the people of Iraq had never heard this recitation. The people of Iraq would recite according to the recitation of Abdullah ibn Mas‘ud radi Allahu anhu, and the people of Sham were unfamiliar with this recitation.
On this basis, these groups would reject each other’s recitation.
This difference caused Hudhayfah radi Allahu anhu to become concerned, so in order to save the Muslim Ummah from discord, he advised Uthman radi Allahu anhu to compile the Noble Qur’an.
Before this, Abu Bakr radi Allahu anhu had compiled the Qur’an.
In that compilation, the verses were arranged, but the surahs were not in order, and they were written separately; furthermore, some abrogated verses were also included.
Uthman radi Allahu anhu compiled it in the form of arranged surahs.

➋
During the caliphate of Uthman radi Allahu anhu, the Noble Qur’an was written according to the following guidelines:
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Only those verses whose Qur’anic status was established by tawatur (continuous, mass transmission) were written.
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Those verses whose recitation had not been abrogated and which were recited in the final period were included.
Verses whose Qur’anic status was based on a solitary report (khabar wahid) and whose recitation had been abrogated were not written.
Some of the Companions radi Allahu anhum ajma‘in had written explanatory notes in their personal codices; these were also removed.

➌
Six copies of these codices were prepared and sent to different regions, and with each one a teacher was sent. The details are as follows:
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One codex was kept in Madinah Tayyibah, and Zayd ibn Harithah radi Allahu anhu was appointed as the teacher.
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One copy was sent to Makkah Mukarramah, and Abdullah ibn Sa’ib radi Allahu anhu was appointed there for teaching.
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One codex was sent to Sham, and Mughira ibn Abu Shihab radi Allahu anhu was designated for teaching in Sham.
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One transcribed Qur’an was for Kufa, and there Abu Abdur-Rahman al-Sulami would teach it.
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One Qur’an was designated for Basrah, and there Amir ibn Qays was appointed to teach the people.
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One codex was kept by Uthman radi Allahu anhu for himself, which was called the Mushaf Imam.
Uthman radi Allahu anhu, at the time of writing these codices, adopted such a method that allowed for the full range of the seven ahruf (modes of recitation).
No dots or vowel marks were placed in them.
The script accommodated various recitations; for example:
In Surah al-Baqarah, “nunshizuha” was written as “nunshiruha” so that it could be read with both the letter zay and ra, according to both recitations.
And those recitations which could not be accommodated in the script were written in different codices; for example:
In Surah al-Tawbah:
﴿جَنَّاتٍ تَجْرِي تَحْتِهَا الْأَنْهَارُ﴾ — in the codex sent to Makkah, it was written as ﴿جَنَّاتٍ تَجْرِي مِن تَحْتِهَا الْأَنْهَارُ﴾, i.e., with the addition of “min.” Thus, in the recitations of Ibn Kathir al-Makki, there is the addition of “min.” Similarly, other recitations were preserved. However, where there was a difference in the writing of words, it was instructed that it be written according to the dialect of Quraysh. Thus, this difference occurred only in one place: whether “al-tabut” should be written with a round ta or a long ta. It was written with a long ta, “tabut,” according to the idiom of Quraysh.
And Allah knows best.