I’d like to address an argument that I hear often about the credibility of the bible. Many people assert that the bible’s credibility about so many events (such as fulfilled prophesies, the life/death/resurrection of Jesus, etc) is non substantial because there exist few extra-biblical sources of these alleged supernatural events. Not to say that the historical events in the bible didn’t happen, i.e. the Jewish exile from Jerusalem. But to use the prophesies made in the bible to prove events recorded later in the same work is considered by many a circular argument. In other words, using the bible to prove itself is a weak argument.
However I would like to present this idea. The bible itself is not one book, but a collection of 66 different books, written by 44 different authors, over a period of 1500-2000 years. It is a compilation of volumes assembled into one book over a period of time, first the Old Testament as the standard Jewish bible before the birth of Jesus, and later the New Testament about 400 years later due to the efforts of the Roman emperor Constantine, the council of Nicaea, etc. I believe if one book asserts a certain bit of information, and a different book written by a different author in a different time period verifies that information, that is a valid comparison.
That would be like people claiming the same facts in different issues of Time Magazine, written by different authors decades apart, are not substantial because they both appeared in Time Magazine. Assembling the books into a compilation doesn’t discredit the information one bit.
And if you’re wondering about the variations of the text that could have taken place over time (mistranslations, deliberate editing, the game of telephone that changes as the story is re-told a thousand times), after studying much about the ancient Jewish culture, it seems this is considerably unlikely or virtually non-existent. The ancient Hebrews took their culture very seriously – and very meticulously. Before the texts were actually written down and were passed on by word of mouth, it was frowned upon to alter the core of the story in any way. Slight details and nuances were acceptable to change, depending on the characteristics of the storyteller, but the core work was always intentionally kept intact. And they had their entire population telling the same stories, so any variations would have been noted and corrected simply by the vast amounts of people who already knew the correct story.

And once the text was finally written down in the original Hebrew or Aramaic (Old testament) or original Greek (New testament), only the most educated scribes were tasked with meticulously transcribing every character. And the review process was exhaustive, so that there was a near 100% accuracy of each new text. Even if one character was found to be erroneous, the entire text was thrown out and destroyed. Not to mention that every time the endless oceans of Middle Eastern sand cough up an older version of any part of the bible, the accuracy compared to the previously older versions is near 100%.
So with all that, I think that it is a valid argument to use different books of the bible, written by different authors at different time periods, to prove facts or assertions also found within the bible.