Quran has not been preserved
A common Muslim statement is that the Quran has been perfectly preserved, unchanged word-for-word, letter-for-letter. We can see that this is false. Caliph Uthman (the third Caliph - Mohammad died in 632 AD, Uthman was Caliph in 644) had a problem on his hands with what was being recited at the time - disagreements and variations in their texts. Already by the time he had come, the memorization of the Quran was failing. He had ordered the compilation of a standard Quran and the complete burning of all other existing copies as there was no agreement on even how many surahs it should contain. One point of contention however is that this included burning the Quran from those that Mohammad had said to learn the Quran from:
Sahih al-Bukhari 3808
`Abdullah bin Masud was mentioned before `Abdullah bin `Amr who said, "That is a man I still love, as I heard the Prophet (ﷺ) saying 'Learn the recitation of Qur'an from four from `Abdullah bin Mas`ud -- he started with him--Salim, the freed slave of Abu Hudaifa, Mu`adh bin Jabal and Ubai bin Ka`b."
From this, what the Quran should contain differs:
- Uthmans version has 114 surahs
- Abdullah ibn Mas'ud has 111 surahs
- Ubayy ibn Ka'b has 116 surahs
One example of what has been removed from the Quran comes from Mohammads wife 'Aishah:
Sunan Ibn Majah 1944
It was narrated that 'Aishah said: "The Verse of stoning and of breastfeeding an adult ten times was revealed, and the paper was with me under my pillow. When the Messenger of Allah died, we were preoccupied with his death, and a tame sheep came in and ate it."
Which is nowhere to be found in the Quran. Unfortunately a goat ate it. Note: Sunan Ibn Majah 1944 is a Hasan rating, while Bukhari is Sahih.
Still not convinced? See common rebuttals
Rebuttal: Uthman standardized the text to prevent discord, based on the dialect of Quraysh (Muhammad's tribe) and what was confirmed by the final review with Gabriel. The destroyed copies were non-standard or contained personal notes.
Response: This implies that prominent companions who learned directly from Muhammad had "non-standard" Qurans. Abdullah ibn Mas'ud, praised by Muhammad for his Quranic knowledge, reportedly had a codex that differed (e.g., lacked Surahs 1, 113, 114) and resisted Uthman's order. This suggests a more complex and less uniform early textual tradition.
A Christians View
The Quran has without a doubt not been preserved, with multiple examples having been given. You may then find the history of the Bible's preservation compelling. The New Testament is supported by thousands of ancient manuscript copies from different parts of the world, with some fragments dating to within a generation of the original writers. This wealth of evidence allows scholars to be very confident about the original text. Rather than a single Caliph standardizing one version and destroying others, the Bible's text is confirmed by a multitude of sources that show remarkable consistency over time.