Do the scriptures contain all that mankind needs for redemption unto salvation? Is there something more that I need besides the Bible? Do I need the wisdom of men? Do I need a personal revelation? According to Paul, the word of God amply supplies all that I need. Nothing else is required or even recommended.
"All Scripture is inspired by God and profitable for teaching, for reproof, for correction, for training in righteousness; so that the man of God may be adequate, equipped for every good work." (2 Timothy 3:16-17)
Unfortunately, the New American Standard Version does not well represent the meaning as set forth in the original language of our New Testament. Specifically, the word adequate in verse 17 is a bit feeble. The King James version translates it much more powerfully and accurately as thoroughly furnished, and the New International Version says thoroughly equipped. Literally, the Greek word "exartizo" means to equip fully, as one would equip a teacher, and to equip thoroughly over time. This is the idea of what the Bible provides us - a complete set of equipment for salvation. Thus the Psalmist writes of his confidence in God's word to save,
"May Your lovingkindnesses also come to me, O LORD, Your salvation according to Your word." (Psalm 119:41)
Paul clearly believed in this power, being eager to preach the word and expressing its power to save to those in Rome and in Corinth,
"So, for my part, I am eager to preach the gospel to you also who are in Rome. For I am not ashamed of the gospel, for it is the power of God for salvation to everyone who believes, to the Jew first and also to the Greek." (Romans 1:16)
"For the word of the cross is foolishness to those who are perishing, but to us who are being saved it is the power of God." (1 Corinthians 1:18)
John also expresses this truth, writing so that we will know that we have eternal life secure. This plainly implies that when I read what the apostles wrote about salvation and God's plan for me I can gain the same confidence of the first century Christians who read this.
"These things I have written to you who believe in the name of the Son of God, so that you may know that you have eternal life." (1 John 5:13)
"Therefore many other signs Jesus also performed in the presence of the disciples, which are not written in this book; but these have been written so 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)
The things written in the Bible were written with the specific purpose of bringing about salvation by faith in Christ. Denying that fulfillment is tantamount to saying that Jesus and His apostles failed at what they intended to do. I'm not prepared to call the work of Calvary a failure, nor the power of the Holy Spirit working through the apostles.