Thank you for the question on the transmission of the Bible, “Is the Bible God’s word, or has it been changed or corrupted over time?”
Dr. Daniel Wallace is the executive director of the Center for the Study of New Testament Manuscripts (The Center for the Study of New Testament Manuscripts), an institute whose initial purpose is to preserve Scripture by taking digital photographs of all known Greek New Testament manuscripts.
Based on his analysis of the text, there are copying errors of the New Testament. By copying errors, many of them are transposition of letters, deletions of letters. For example, the word, church may be spelled churk, curch, kurch, or some other variation of it. However as a person reads the sentence, one can likely see that the word is misspelled since they didn’t have erasers in their copying. They attempted to be careful as possible.
Thus when the Dead Sea Scrolls was discovered in 1947, dating to 2nd or 1st BCE, compared to younger manuscripts, the differences are minimal. There is 98% to 99% similarity as in the scroll of Isaiah. Scholars have carefully examined every letter in the Old Testament and New Testament, comparing it with other manuscripts.
Granted that the Old Testament can only be compared back to the 2nd Century BCE, but the careful copying from that period to the 1500 CE reflects not a careless of copying or random adding of new materials or deletions of wholesale sections of a scroll but an exactness to it.
Can one say absolutely that there wasn’t major corruption from an earlier text? No, but the likelihood is not since the Jews and the Christians believed that they were copying the very Words of God. Great care in copying it.
It is similar as one copying the US Constitution. One would take great care in copying the exact words, avoiding interjecting their own opinions into the Constitution. That would be interpreting the Constitution, not copying the Constitution.
The reader has to decide whether s/he believes that the Scriptures have been carefully preserved by copyists. Comparison of scrolls have led textual critics to formulate their opinion as to the nuisances of a word or the spelling of a word.
SUMMARY: One can conclude that the Scriptures is 98% accurate/similar to the 2nd BCE. Beyond that date would be a step of faith unless further discoveries are made.