How do we know the message of the gospel is about Christ?

Throughout Scripture, we find that the ultimate purpose of the law, the prophets, and the writings is to testify of Jesus Christ. Jesus Himself emphasizes this in Luke 24:44, where He affirms that all things written about Him must be fulfilled. This indicates that interpretations of Scripture that separate the Old Testament from the New Testament fail to grasp the cohesive revelation of Christ as the focal point of God's salvific plan. Scriptural narratives and visions, as seen in the likes of Zechariah, serve not just as historical accounts but as pointers to the Person and work of Christ, culminating in the New Covenant established through His sacrifice.