If you want to know what you have to do to receive eternal life, what book of the Bible should you turn to? This question has divided scholars and laypersons alike. However, it doesn't need to be a lightning rod question. Scripture itself gives the answer. All of the Bible is valuable in helping a Christian grow, but there is a book whose stated purpose extends beyond discipleship training. Only a single book in the entire Bible has a clearly stated evangelistic purpose statement.
In fact, there is only one book with the stated purpose of converting them to become believers. This comes as a surprise to many since Gospel presenters often uproot verses from all over the New Testament in order to present their version of the good news. Notwithstanding, Only one book in the Bible has this specifically stated intention: making believers out of its readers. Note this concise and intentional statement that appears at the end of the Gospel of John.
And truly Jesus did many other signs in the presence of His disciples, which are not written in this book; but these are written that you may believe that Jesus is the Christ, the Son of God, and that believing you may have life in His name. (John 20:30-31)
John points out that he could have written much more about Jesus, but he has done something unique in choosing which stories he recorded. He has created a curated collection of occurrences and claims. Of first importance, John claims that it is on the basis of belief that a person has eternal life.1 There is a claim that a person must believe in order to have eternal life.
This means his Gospel contains the entirety of the message that needs to be believed in order to have eternal life. John effectively says that a person who is seeking eternal life need only read his Gospel. If the reader believes what is in the Gospel of John, they therefore have eternal life. This within itself bears repeating.
Often when I explain the idea that the whole Gospel message is contained in John alone, grumblers respond, "I prefer to consider the whole counsel of scripture." This is basically a way of saying, "I don't believe John's Gospel is enough to get a person saved." The author of John strongly disagrees in his purpose statement mentioned above.
I don't put much stock in extra-biblical creeds, but I find it interesting that even the Westminster Confession acknowledges that one doesn't have to consider the entirety of the Bible to know how to get saved when it states,
…Those things which are necessary to be known, believed, and observed, for salvation, are… clearly propounded and opened in some place of scripture or other...2
The confession expresses the idea that you don’t have to read through all 31,000 verses of your Bible to know how to get saved. A portion or a part is all that is required concerning salvation. John tells us that the portion of the Bible that absolutely contains the saving message is His Gospel. The Gospel of John is the section of the manual for receiving eternal life.
In his one-volume commentary on the entire Bible, Dr. Radmacher talks about how some consumer product manuals have a section titled "Read This First." It's a section that should be read even if every other part of the manual is ignored. He explains that this is how we should look at John’s Gospel. Read John’s Gospel first. If you read nothing else, read John’s Gospel. He argues that it ought to be read and understood first before any other books are considered.3
I have a friend who sometimes writes long emails. At the end of the email, he summarizes his emails with a section he calls TLDR. It stands for Too Long Didn't Read. In that section, he gives the important information. If you read that section and ignore the rest, you'll have the essentials. John's purpose statement that we read a moment ago acts as the Bible's equivalent. John’s Gospel is a type of TLDR. If you read only John, you may not know everything the Bible has to offer, but you will have the essentials.
Of course, all scripture is valuable, but John is the “read this first” or the TLDR section of the Bible. It contains the essential obligation that must be fulfilled in order for one to be saved.
After coming face to face with John's purpose statement that we looked at a moment ago, virtually no one could legitimately disagree that John's Gospel contains the entirety of the saving message. Some wish to bypass the pages of the Gospel of John, but I have serious questions about the motives of anyone who does. It seems incredibly misguided, considering that John has carefully crafted a Gospel presentation that guarantees eternal life to anyone who reads and believes it. The motivation to skip over the message of John and dive into the Epistles, Synoptics, or even the Old Testament, seems to be an attempt to evade the simple truth John presents. As many scholars have noted, John's is the only book in the Bible that states its purpose clearly and succinctly: It was written to tell individuals how to find eternal life.4
Not only is the Gospel of John the Bible's only book with an expressly stated evangelistic purpose statement, but it is also the most accessible book of the Bible to understand, both in English and in the original language. Many scholars have described John as simplistically worded.5 Unlike the first three Gospel writers and the writers of the New Testament letters, John uses a small and straightforward vocabulary—just six hundred Greek words.6 When Greek students are studying the ancient language, they are often assigned passages from John first for these reasons. John's consistency echoes through the book from beginning to end. He uses essential terms in a technical, not an ambiguous way. He defines his terms internally so that the reader knows all they need to know by the end. He makes his purpose understandable and delivers on that purpose. The Gospel of John contains the entire Gospel message that one must believe in order to have eternal life. A person can read it, and it alone. If they believe what they read, they will be spiritually immortal, possessing eternal life, by the end of the book.
Thus, the place where one must look for the living water, that is the saving message, is in the Gospel of John. For the reader, the Gospel of John is the fountain of life.
1 Though, here, John uses the abbreviation “life” it’s clear from the body of the Gospel that he is referring the Jesus’ promise of “eternal life.”
2 Westminster Assembly, The Westminster Confession of Faith: Edinburgh Edition (Philadelphia: William S. Young, 1851), 19.
3 Earl D. Radmacher, Ronald Barclay Allen, and H. Wayne House, Nelson’s New Illustrated Bible Commentary (Nashville: T. Nelson Publishers, 1999), 1307.
5 Gerald L. Borchert, John 12–21, vol. 25B, The New American Commentary (Nashville: Broadman & Holman Publishers, 2002), 318.
6 Robert N. Wilkin, “The Gospel according to John,” in The Grace New Testament Commentary, ed. Robert N. Wilkin (Denton, TX: Grace Evangelical Society, 2010), 358.