We know that the Bible often quotes itself. This might seem narcissistic if it was written by one author, but since it was written by 40 authors and is more like a library of books (containing many genres and writings styles) than a single book, this cross-referencing makes more sense. After all, we see authors often cite and quote other authors that have written on the same subject all the time. So how many times in the Bible does an author reference an earlier passage from the Bible? The answer is staggering: 63,779 times. Given that the Bible is compiled of 66 books, with at least 40 different authors, over the time period of about 1,500 years, all of which took place before the printing press and mass production of documents...that's actually really incredible. It makes me really consider the role that the Holy Spirit had in inspiring and guiding the authors in their work.
I once read a book that made the footnotes available as a download because there were so many of them, the footnotes were longer than the book itself, and the publisher was basically like, it doesn't make sense financially to print all of these notes. Give it to people electronically if they want all that. Point is, the more scholarly the work, the more likely it is to have a robust footnote section and/or appendices (assuming the author is happy to actually cite their sources and wants their readers to be able to dig deeper and check their work). This graphic is very much an illustration of what it would look like if you drew all the cross-reference footnotes in the Bible as arcs. This illustration is a bit of what scholarship looks like. And to think there are still skeptics out there that think these authors were ignorant, illiterate people for whom a wheelbarrow would have been impressive technology (Sam Harris). Perhaps they deserve a bit more credit than that.
In addition to the authors of the Bible composing written predictions for the future that turn out to be correct (a conservative estimate puts the number of prophecies about Jesus from the old testament at over 300, all of which came true), writing accurate descriptions of current events and past events at the highest level, and even writing about past events so distant that they would have had no way of knowing or validating them (consider the writings of creation events from Genesis 1, which correctly states the initial conditions of the primordial earth as well as lists 10 acts of creation in the correct scientifically chronological order - Dr. Hugh Ross). They also knew the writings that came before them that could be trusted as the Word of God and the others that could not be trusted. They knew those writings well, scrutinized them heavily, and they used those that passed the tests. They expanded upon them and provided greater insight. If they hadn't done that, we would have a collection of disparate and largely disconnected works each with their own perspective and motivations, much like a normal library does. Instead what we have in the Bible is this compilation of works that weave together like an elaborate tapestry that displays evidence of having been overseen by someone who transcends the space and time in which these writings were made. There is a grand design at play in the Bible.
The graphic above is a visualization put together by Chris Harrison with the research provided by Christoph Römhild. Every book in the Bible is represented by the bar graph running along the bottom, each book alternating between light and dark grey. The light and dark grey bars at the bottom represent each verse, the height of those bars correlating to the length of the verse itself. The colored lines arching over the top connect each verse that refers to another verse and are color-coded by the distance between the two relevant verses.
I'm really impressed with this project and with how well it illustrates for us how connected the various parts of the Bible are. The Bible is a collection of works that is nothing short of miraculous in so many ways, and this graphic gives us a very accessible image of one of those ways.
If you're interested to see the original source of the graphic and to learn more about Chris Harrison's other work, I'd strongly encourage you to visit his site here. He's got some really incredible work there. I hope that this piece will help to strengthen your faith in the reliability of the Bible as well as give you a sense of the incredible lengths and effort to which our Creator went to reach us.