Is there a reason why the Bible has many repetitions, e.g. the gospels of Luke, Mark, Matthew, etc., and also repeated verses found throughout the Bible? Do the verses mean they more important repeated more often throughout the Bible when compared to a single verse? Is there a divine reason why there is repetition in the Bible, instead of it being a concise book?
There are a variety of reasons why the Bible contains repetitions.
"If I bear witness of Myself, My witness is not true" (John 5:31). A single person's word is not a witness to truth because you have no means of verifying the validity of what he stated. The Bible is the collection of about forty different writers who came from a wide variety of backgrounds and across a time period that exceeds 1,500 years, yet they state a single message. The statements, seen from different viewpoints, gives us credible witness to the events they record.
Some, like the coming of the Son of God, is incredibly important and needs solid testimony. Even with the eyewitness accounts recorded by four different authors, we still have people today trying to undermine the truth they presented. It is the fact that the accounts come from different viewpoints that makes them difficult to pull down. Matthew wrote to a Jewish audience from a Jewish point of view. In a way, it is ironic because as a tax collector for the Romans, he was an outcast in Jewish society. Mark wrote for a Roman audience; yet, he was a very young man when the events happened and it is agreed that he was recording Peter's account of the events. The Romans weren't impressed by the Jews, but the witness aimed at their viewpoint was the apostle to the Jews. Luke wrote for a Greek audience. He was meticulous in getting details and interviewing eyewitnesses. His account is not a single viewpoint but a composite of many witnesses pulled together. John wrote for Christians. He focused on the discourses and teachings of Jesus. Each account gives us a good view of Jesus, but together we get a more complete view. Each account varies slightly in the details recorded, not in a way that contradicts, but because they were looking at the same events from different views. Between them they support the facts of what happened.
The Old Testament also has something similar, the records: I Samuel, II Samuel, I Kings and II Kings are repeated in I Chronicles and II Chronicles. The first set is told from a historical point of view. The second set is told from a religious or priestly point of view.
The Bible also contains repeated stories, accounts of single events that are contained in several places. For example, events from Hezekiah's reign appears in II Kings 18-20, II Chronicles 32, and Isaiah 36-39. The accounts in II Kings 18-20 and Isaiah 36-39 are so similar that it is clear that Isaiah wrote both. Jeremiah 52 and II Kings 25 are nearly word for word the same, telling us that Jeremiah wrote both of these. These repeats help tie the various books together. If we accept one book, then we should accept the other as well since it comes from the same authors. But the repetition also gives us a way of measuring the accuracy of the copying done over the centuries. Scribes make mistakes, but unless someone was trying to purposely alter a story, the same mistake will rarely occur in two different contexts.
But probably the real reason for the repeats is that each book is a complete story by itself. But several books overlap events in history, so the common points are repeated. Cross-referencing with scrolls would not be easy and division of the text into chapters and verses did not come until long after the Bible was written. Thus you find the Ten Commandments given in Exodus 20 in the account of the actual event and again in Deuteronomy 5 as Moses reviews before his death what God has done for Israel.
Some events are repeated because multiple authors touch on the same time period. This is what often confuses people regarding Genesis. It is a collection of eleven records. Since each tells his account by placing it in history, there are overlaps between the start and end of each account. Genesis 1:1-2:4 is God's account of the creation. Genesis 2:4-5:1 is Adam's account of his life, starting with the creation. Genesis 5:1-6:9 is Noah's account which is mostly a genealogy of his family but ends with the flood. Genesis 6:9-10:1 is Noah's sons account which starts with the flood and ends with the dividing of the nations. And so on.
Some repeats are summaries of prior events, often told in a different form. Psalms 104 contains a poetic account of the flood. Psalms 105 is an account of the Exodus in the form of a psalm. The summaries help keep the events in context and make memorization easier. But they also serve as checks on transmission of the text. There have been many who have tried to alter the Bible's message by changing words here and there to make it say something different. These alterations are often easy to spot because people rarely are able to find all the references and the alterations don't work in the different writing forms. The alterations cause contradictions to appear and the glaring errors tell us that the work is not accurate.
When sentences are repeated in a row that is the old way of emphasizing a point. They didn't use bold fonts or italic letters to do emphasis. Remember that these were hand written documents; bold and italics don't transmit well in handwriting. Nor did they use underlining or even punctuation as we now do. Writing in ancient days was much more condensed because material was expensive. Thus to emphasis a point, it was repeated, such as Paul's point about not altering the Gospel: "But even if we, or an angel from heaven, preach any other gospel to you than what we have preached to you, let him be accursed. As we have said before, so now I say again, if anyone preaches any other gospel to you than what you have received, let him be accursed" (Galatians 1:8-9).
Statements may also be repeated in different context to get you to think more about the meaning. Sometimes we see things differently when we are presented with an idea in light of different thoughts. The book of Proverbs does this heavily. The same idea may be said several times. Sometimes it is just in a different category of topics. Compare Proverbs 20:16 and Proverbs 27:13. Sometimes the wording is presented just slightly differently. But the purpose remains the same: to get the reader to think. "To know wisdom and instruction, to perceive the words of understanding, to receive the instruction of wisdom, justice, judgment, and equity; to give prudence to the simple, to the young man knowledge and discretion -- a wise man will hear and increase learning, and a man of understanding will attain wise counsel, to understand a proverb and an enigma, the words of the wise and their riddles" (Proverbs 1:2-6).
Then there are quotes. Later writings will quote earlier statements to show how what was stated before was fulfilled later. For example, "For this is he who was spoken of by the prophet Isaiah, saying: "The voice of one crying in the wilderness: 'Prepare the way of the LORD; Make His paths straight'" (Matthew 3:3). Statements are also quoted to show that what might have been seen as something of limited application does have broader implications. "For it is written in the law of Moses, "You shall not muzzle an ox while it treads out the grain." Is it oxen God is concerned about? Or does He say it altogether for our sakes? For our sakes, no doubt, this is written, that he who plows should plow in hope, and he who threshes in hope should be partaker of his hope" (I Corinthians 9:9-10).
Sometimes the same thing is stated multiple times, but using different words. One reason is for poetry. The Hebrews used a form of poetry where ideas are compared and contrasted instead of the rhyming or repeating of sounds. It is an amazing form of poetry because it can be translated into any language and retains its form. "Blessed are the undefiled in the way, who walk in the law of the LORD! Blessed are those who keep His testimonies, who seek Him with the whole heart!" (Psalms 119:1-2). The repetition but with different words allows one statement to help define the other. This is important in language because words come with varying meanings and implications. Two wordings of the same idea refines the idea more precisely. It keeps people from assigning too narrow or too broad of a meaning to what is said.
At other times, ideas are repeated but in the negative for the same purpose. "He who has a slack hand becomes poor, but the hand of the diligent makes rich" (Proverbs 10:4).
Ideas are also repeated when different audiences are addressed. Thus when Paul wrote letters to both Ephesus and Colosse, they had different themes, but covered similar topics. Compare Ephesians 4:31-32 with Colossians 3:8, 12-13. Each letter is a complete set of instruction by itself. But having the repeats creates a way to check for attempts at altering the message, as well as giving a way to see the ideas in slightly different lights to get a more accurate understanding of what is being expressed.
When you don't have varying fonts and punctuation at your disposal, repeated words become the way to give emphasis. "Jesus answered and said to him, "Truly, truly, I say to you, unless one is born again he cannot see the kingdom of God"" (John 3:3 NASB). Unfortunately many translations alter these repeated words into superlatives, so you don't see them as often as they appear in the original text: "Jesus answered and said to him, "Most assuredly, I say to you, unless one is born again, he cannot see the kingdom of God"" (John 3:3 NKJV).
Repeating a word three times is equivalent to saying something with bold letters, underlined and followed by exclamation points. "And one cried to another and said: "Holy, holy, holy is the LORD of hosts; The whole earth is full of His glory!"" (Isaiah 6:3). Or, "And I looked, and I heard an angel flying through the midst of heaven, saying with a loud voice, "Woe, woe, woe to the inhabitants of the earth, because of the remaining blasts of the trumpet of the three angels who are about to sound!"" (Revelation 8:13).
Words can be repeated as markers. For example, in I Corinthians Paul uses the word "now" when he is about to switch to a new topic (I Corinthians 7:1, 25; 8:1; 12:1; 16:1). Paul also uses "for" frequently to mark the points in his arguments, similar to today's use of bullet points.
Ironically, it is because of its use of repetition that the Bible contains far more than it might first appear. For a book that has such depth of meaning and such precision, it is presented in a form that far more concise than what men tend to write. You need only look at our laws, tax codes, or history books to appreciate the remarkable briefness of God's word.