The Scriptures testified to Jesus; their promises were fulfilled in his life, death and especially his resurreciton. The biblical-theological and hermeneutical task is to try to discern how the realtionship of Jesus and the gospel to the Old Testament was understood by Jesus, the apostles and the New Testament authors. The relationship of Jesus to the Scriptures was not obvious to everyone, and it was really problematic for the Jews and even for the disciples. This relaitonship of the texts to the person and work of Jesus is central to the unity of the Bible.
Graeme Goldsworthy, Christ-Centered Biblical Theology: Hermeneutical Foundaitons and Principles, page 52