Uthman summoned Zayd bin Thabit, Abdullah bin Zubayr, Saeed bin As, and Abdul-Rahman bin Harith bin Hisham, and they copied it into the official codices. Uthman said to the three men from Quraysh, "Whenever you and Zayd bin Thabit disagree on any part of the Quran, write it in the dialect of Quraysh, for it was revealed in their tongue." So they did just that.
أن عثمان دعا زيد بن ثابت، وعبد الله بن الزبير، وسعيد بن العاص، وعبد الرحمن بن الحارث بن هشام، فنسخوها في المصاحف، وقال عثمان للرهط القرشيين الثلاثة: إذا اختلفتم أنتم وزيد بن ثابت في شيء من القرآن فاكتبوه بلسان قريش، فإنما نزل بلسانهم، ففعلوا ذلك.
Bukhari related it in the Book of Virtues (3506) from Abdul-Aziz bin Abdullah, who said, "Ibrahim bin Saad told us, from Ibn Shihab, from Anas," and he mentioned it. Bukhari also related it in the Book of the Virtues of the Quran (4984) through another route from Anas, in which it states, "Uthman said to them, 'If you and Zayd bin Thabit disagree over any Arabic wording of the Quran, write it in the dialect of Quraysh.'"Tirmidhi related it (3104) through another route, from Ibrahim bin Saad, with his chain. Zuhri said, "They disagreed that day over 'tabut' and 'tabuh'. The Qurayshis said 'tabut', while Zayd said 'tabuh'. Their disagreement was referred to Uthman, who said, 'Write it as tabut, for it was revealed in the dialect of Quraysh.'" Its isnad is sahih, and this is more sahih than the report of those who said that Zayd's reading, meaning "tabut", was chosen because he used to write down the revelation. Dani considered "tabut" to be part of Zayd's reading. See Muqni (14–15).In summary, the writing down of the Quran went through three stages.The first, the noble Quran was written down during the lifetime of the Prophet ﷺ in scattered portions, according to the general reading that the Prophet ﷺ taught his companions, without the other modes in which Allah permitted the Quran to be recited as a facilitation for the people. For it is self-evident that the Prophet ﷺ would dictate to the scribes of revelation what had been revealed to him of the Quran in a single mode known to his companions who were close to him. Teaching, however, was different, for he ﷺ would teach whoever came to Madinah from various tribes in a mode familiar to them, one of the seven modes (the seven dialects) known throughout the Arabian Peninsula. Someone from the people of Madinah might also be present at such a gathering, and he too would have yet another mode. Consequently, some of the companions wrote down what they had of the Quran according to other modes. The Prophet ﷺ did not depart this world until he was satisfied that what was in people's hearts matched what was in his own heart and what was recorded on the written tablets.