There is, in the end, only two ways to read the Bible: is it basically about me or basically about Jesus? In other words, is it basically about what I must do, or basically about what he has done? If I read David and Goliath as basically giving me an example, then the story is really about me. I must summons up the faith and courage to fight the giants in my life. But if I read David and Goliath as basically showing me salvation through Jesus, then the story is really about him. Until I see that Jesus fought the real giants (sin, law, death) for me, I will never have the courage to be able to fight ordinary giants in life (suffering, disappointment, failure, criticism, hardship). For example how can I ever fight the ‘giant’ of failure, unless I have a deep security that God will not abandon me? If I see David as my example, the story will never help me fight the failure/giant. But if I see David/Jesus as my substitute, whose victory is imputed to me, then I can stand before the failure/giant. As another example, how can I ever fight the ‘giant’ of persecution or criticism? Unless I can see him forgiving me on the cross, I won’t be able to forgive others. Unless I see him as forgiving me for falling asleep on him (Matt.27:45) I won’t be able to stay awake for him.
In the Old Testament we are continually told that our good works are not enough, that God has made a provision. This provision is pointed to at every place in the Old Testament. We see it in the clothes God makes Adam and Eve in Genesis, to the promises made to Abraham and the patriarchs, to the Tabernacle and the whole sacrificial system, to the innumerable references to a Messiah, a suffering servant, and so on.
Therefore, to say that the Bible is about Christ is to say that the main theme of the Bible is, ‘Salvation is of the Lord’ (Jonah 2:9).