Jesus said: “You search the Scriptures because you think that in them you have eternal life; and it is they that bear witness about me” -John 5:39
If you really want to understand the bible, you need to first understand that the whole bible is about Jesus. It’s about Jesus as substitute, and Jesus as representative. There was that first representative of humanity, that was Adam. 1 Cor 15:22 says that “in Adam all die, so also in Christ shall all be made alive.” What Paul is saying there that all who have Adam as their representative before God don’t have eternal life, and all who have Jesus as their representative before God have eternal life. That representation is called “federal headship” by theologians and it’s a big theme in the bible. It’s how we who are in Christ receive forgiveness of sins because of His death on the cross, because He represents us as a substitute. He took the punishment due our sins. That means he atoned for our sins on the cross.
Jesus said: “You search the Scriptures because you think that in them you have eternal life; and it is they that bear witness about me” -John 5:39
He also represented us in His life lived. In John 5:36 Jesus says that God the Father gave him some works to accomplish, and he was doing them. We read in Gal 4:4-5 that He was born under the law to redeem those under the law, and in Matt 5:17 that He came to fulfill the law, or in Matt 3:15 to fulfill all righteousness. In 1Cor 15:45-47 Jesus is called the last Adam, and the second man. This gets us to the whole point of the bible. Jesus is that promised seed of the woman back in Gen 3:15. He came to succeed in obeying where the first Adam failed. His successful completion of obeying God perfectly as the representative of all those who put faith in Him secured an indefectible status of righteousness before God. Therefore He secured our peace with God and the way back to the tree of life, which is to say eternal life.
So, the whole bible is about how Christ as that second and last Adam successfully completed what the first one failed to. He did this through a life of perfect obedience under the law all the way to death, so at His death, we who He represented inherit life. He was raised again by the Spirit, vindicating Him. That is to say that He as that last Adam was declared righteous, and given the eternal life and blessings promised for the fulfillment of that first covenant. So, we who have Christ as our federal head are adopted as first born sons of God in Him (Gal 4:5), and we too will be raised again (2 Cor 4:14).
That is what the bible is all about. That is the meta-narrative, the overarching doctrine that ties the whole bible together as one message, one story, one “good news” to proclaim. All the things in the bible are either types, or they point us to Christ, or our need of Christ. So much of the Old Testament is a picture of that, it’s why we see it as “redemptive history”. In the bible we see that Christ came to be the representative man living the life of loving God and neighbor perfectly, and dying the death on the cross that we who fail to obey God perfectly deserve. So Christ is our representative in life and in death. If you rest your faith in Him, and in the promise that He secures your salvation by His own works and sacrifice, the bible declares in 1 John 5:13 that “you have eternal life” . That’s what it means to have faith in Christ, and the more we understand about what He accomplished, the greater and more firm our faith is. This is why we continue to proclaim the good news of what Christ accomplished, not only to the world, but to ourselves. That is our hope, that is the story of the bible. It is one message, it all points to one person, and His work, and His accomplishments on behalf of all those He represents.