A Christian friend was saying that he knows that the bible has been changed throughout the years, he was also saying that the Quran has also been changed since it was revealed many years ago. (He’s not knowledgeable about Islam and I believe this is his assumption). What can I say to counter this?

Ustadh AbdulAziz al-Haqqan

Let him open any book of knowledge throughout the years even the oldest where are the changed ayat? he will find all the quotations are the same throughout 1400 years of Islamic scholarship, so how did it change? With other books we find throughout the years and books differences.