One of the major developments of the Protestant Reformation was the return to Scripture as supreme authority. The Reformers coined the phrase sola Scriptura (Scripture alone) to summarize this conviction. To rightly understand the Reformers conviction that Scripture is our highest authority, we need to understand what the Scriptures are, how God authored the Scriptures, and what Jesus said in regard to them.
The Scriptures are the expression of God’s mind given to us in written form. The term Scripture means sacred writing and the word Bible comes from the Greek word meaning book. Therefore the Scriptures are a book of God’s sacred writing. It’s a collection of 66 books, written in three different languages (Hebrew, Greek, Aramaic) written from 3 different continents (Asia, Africa, Europe) over a span of fifteen hundred years (from about 1450 B.C. to about A.D. 90) by over forty different authors. These people were not alike. They came from various levels of society and from very diverse backgrounds. Some were kings; others were statesmen, priests, prophets. There was a fisherman, a tax-collector, a tentmaker and a physician. Their opinions on any other subject would have been as wide and diverse as ours is today. Yet together they produced a volume that is uniquely unified in its message. The message is, in short, a single story regarding the restoration and renovation of the entire material and immaterial universe through Jesus Christ!
Before His death and resurrection, Jesus told the disciples that a day would come when He would no longer be in their presence but that the Holy Spirit would come and would remind them of His life and teachings so that they could write and teach accurately that which Christ accomplished (Jn. 14:25-26; 16:12-15). The Scripture, unlike any other book, is a book written by both God and man. There was a partnership between the Holy Spirit and the human authors as the Spirit guided them in the process. God was working with their unique personalities, their unique backgrounds, unique life experiences, their education, to enable, or to inspire the writing of Scripture in such a way that they wrote all that God wanted them to say without excess or error (2 Pet. 1:20-21, 1 Cor. 14:37). We call this divine inspiration. As one theologian wrote, “The belief that God wrote Scripture in concert with human authors whom he inspired to perfectly record his words is called verbal (the very words of the Bible) plenary (every part of the Bible) inspiration (are God-breathed revelation). Very simply, this means that God the Holy Spirit inspired not just the thoughts of Scripture but also the very details and exact words that were perfectly recorded for us as Scripture.” As Evangelical Christians, we value and love the Scripture; we cannot simply ignore parts of the Bible as primitive, dismiss other sections as culturally irrelevant, or explain them away by human reasoning. Paul tells us, “All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness, that the man of God may be competent, equipped for every good work” (2 Tim. 3:16-17, emphasis added).
The most important reason for believing the Scripture to be the Word of God and the sole authority for Christians in all matters of faith and practice is that this is what the Lord Jesus taught. Jesus highly esteemed the Old Testament; He continually quoted it (Mt. 4:1-11), saw His life as a fulfillment of it (Lk. 4:16-21), and declared, “I say to you, until heaven and earth pass away, not an iota, not a dot, will pass from the Law until all is accomplished” (Matt. 5:18). An iota is the smallest letter of the Hebrew alphabet, so what Jesus was saying was that even the most minute parts of the Mosaic Law are authoritative. Because our Lord Jesus trusted the Scriptures as the Word of God and submitted to it as an authoritative revelation, we do the same.
Scripture is the expression of God’s mind, therefore, we encourage all Believers to memorize, meditate, study and share His truth. We trust the Holy Spirit to use the Scriptures to make us more like Jesus, both individually and corporately as the church.
 Gerry Breshears, Doctrine: What Christians Should Believe, pg. 48. Crossway, 2010