Why God's Book Cannot Contain Error
1. God Revealed it
"Those who disbelieve in the Reminder when it comes unto them (are guilty), for indeed it is an unassailable Scripture. Falsehood cannot come at it from before it or behind it. (It id) a revelation from the Wise, the Owner of Praise" (Qur'an 41:41-42).
"Praise be to Allah* Who has revealed the Scripture unto His slave, and has not placed therein any crookedness (but has made it) straight" (Qur'an 18:1-2).
"Allah has (now) revealed the fairest of statements, a Scripture consistent" (Qur'an 39:23).
"A Qur'an in Arabic, containing no crookedness" (Qur'an 39:28).
2. God Preserves it
God has promised to always preserve His book. He says:
"Surely We, even We, revealed the Reminder [the Qur'an], and We verily are it's Guardian." (Qur'an 15:9).
The Qur'an contains no additions. It remains today letter for letter as it was revealed over 1400 years ago. Nothing added, nothing taken away.
Two of the original manuscripts of the Qur'an prepared 1400 years ago still exist today. One is in the Topkapi Saray Museum in Istanbul, Turkey, and the other in Tashkent, Russia. Both of these are identical in content with the Qur'an available all over the world today.
You Can Examine it !
God says:
"Will they not then consider the Qur'an with care? If it had been from other than Allah they would have found therein much discrepancy." (Qur'an 4:82).