Bart D. Ehrman, The New Testament: A Historical Introduction to the Early Christian Writings (OUP, 2016), 29.
You will sometimes hear someone say that “the New Testament is the best-attested book from the ancient world, so we can trust it.” The first part of this statement is absolutely true, as we have seen. But the second part is riddled with problems. For one thing, even if we had 5 million manuscripts of the New Testament, rather than some 5,700, that would not mean that the New Testament could be trusted. Think about it for a minute. Suppose we had more manuscripts of Plato than of the New Testament. Would that mean that Plato could be trusted more? Even if you knew exactly what he said, does that mean that what he said is trustworthy? Look at it this way: We have the exact words of Karl Marx and of Rush Limbaugh. Does that mean they can be trusted? Trusting the New Testament has nothing to do with whether it is well attested or not.
But beyond that, even though the New Testament is better attested than any other book in the ancient world, there are still problems with knowing what its authors really said. We don’t have a lot of early manuscripts. We don’t have any complete ones until nearly three centuries after these books were written. And there are hundreds of important differences among our manuscripts. Scholars debate numerous passages. There are some places where we may never know what was written.