Christians, why do claims made in the bible, validate other claims made in the same said bible, and how exactly do they achieve this?

That's only evidence of compiled propagated structure refined over time .

The claim that the bible has Stood the test of time is silly . The bible has changed over time and time takes credence from the bible

and does not add to it .

Christians think their book has existed since 325 but back then and for a thousand years later it was called the Latin Vulgate . Protestant books since then number in the thousands and vary in translation and authenticity .

JW Watchtower type interpretations are to the King James version as the King James version is to the Latin Vulgate .

Thank God only one source has the power to change Harry Potter

When I look at say the "Federal Code of Regulations" I have to use the "Federal Code of Regulations" to validate what the "Federal Code of Regulations" is saying.

The study of Christianity is like geometry in a way. In geometry a person uses geometry to validate geometry. While Trig is not Geometry, still the validation is based on Geometry and not chemistry or even history. While Geometry has a historical base the history of Geometry is a separate subject.

So of course it is only logical that the Bible be used to validate other claims in the Bible. While the Bible does not contain all the books possible it does contain internal validation/s because the completed work is actually several peer generated papers which support the common premise.

It does not take any external validation to know that returning evil for evil yields evil. So the statement "Do not return evil with evil" is a stand alone truth. The real validation of what Jesus taught is by practicing it and when the practice yields the stated results the validation of Jesus is a given. After all if some one tells you something and you find it true it validates that person as being qualified as a teacher on that subject.

Not all Christians argue that way.

Primarily through fulfilled Bible prophecy.

The very same way that a claim found in one document

supports or validates (it's usually one OR the other) a similar or identical claim found in another document.

In other words: in exactly the same way(s) that happens in documents other than the Bible.

Christians, why do claims made in the bible [no comma separating subject from verb] validate other claims made in the same said bible, and how exactly do they achieve this?

This is accomplished through witnesses.

One person says something, and then somebody else comes along who heard the very same thing said. So for example,

Matthew says in his gospel that after six days Jesus took Peter, James and John his brother, brought them up to a high mountain by themselves and was transfigured before them etc. (Matthew 17: 1 & 2).

Luke 9 gave the same account of Jesus - he didn't use the word "Transfiguration" but described how Jesus' face was altered when He became white and glistening (Luke 9:27 - 36).

Mark 9: 1 - 13 gave a similar account of the event.

Then along came Peter WHO WAS AN ACTUAL EYE WITNESS OF HIS MAJESTY CONCERNING TO THIS EVENT. He gave his account (2 Peter 1: 16 - 18)

God says in the mouth of two or three witnesses let everything be established. (Deuteronomy 17:6) So that's how it's accomplished

Usually, something is PROPHESIED by one of the old prophets of God in the Old Testament. Then when it comes to pass in the New Testament, it is written up by witnesses, such as all about Jesus' crucifixion. Everything about it was prophesied in Psalms, so when it came to pass, those who wrote it up in the New Testament were the witnesses who caused the truth to be established.

You don't really specify what you mean, so I've addressed it from a few angles.

1) The Bible is not a single resource, but a compilation of different resources from different human authors. If one author agrees the claim of another, that is supporting testimony.

2) Furthermore, overall logical consistency between all the resources written by various human authors over several thousand years, speaks to the influence of a single, overarching, intelligent Source of the information.

3) If that Source thinks something is important enough to repeat, that repetition adds weight to the claim that whatever information is repeated represents the views of the Source.

Because while they were written thousands of years apart they are spot on, in things which there cannot be controlled, like where Jesus was born

Because the Bible is the perfect word of God, and we know this because it says so in the Bible, and it also says in the Bible that God is real, and the Bible is the perfect word of God...