I believe that understanding and knowing the following verse is crucial for us to understand the purpose of Scripture.
2 Cor 1:20 For no matter how many promises God has made, they are yes in Christ.
For it shows us that Christ wasn’t an after thought of God, rather that right from the very beginning, Christ was the central purpose of God’s plans for us. There is a huge theme throughout the Old Testament which says, When you sin, if you turn and seek the Lord your God with all your heart, with all your mind and all your strength, you will receive the desire of your heart.
That is, the promise is that if you desire God, God will give himself to you. And this very great and precious promise has been fulfilled in Christ. Further more, God promises himself in the form of his Holy Spirit. For Peter speaking of Scripture, says that the promise of the Holy Spirit is for all who believe…for now and all who are far off. The promise of the Spirit is that we will cry out to the God, ABBA Father. Within that cry, the promise is complete.
For it tells us that we have received God in all his fullness. We have received the Father, the Son and the Holy Spirit. And the giving himself to us is complete.