The New Testament books are about fulfillment, about promises kept. As Augustine put it, “the Old is in the New revealed.” The climax of the Old Testament is the New Testament. Mysteries are declared, and shadows are swallowed by light. Christians are New Covenant members, yes. But New Covenant believers must not be only New Testament people. We must be whole-Bible people!
A Christian reading of Scripture affirms that the biblical authors do not tell us everything everywhere all at once. Things build, and that takes time. The doctrine of Scripture includes the teaching of progressive revelation.
The Story of God’s redemptive plan is a long story, encompassing sixty-six books and unfolding across millennia. Told in two Testaments, the biblical story is from a Divine Author who has inspired the writings we read therein. Growth in understanding the Scripture will mean paying attention to how the Old and New Testaments relate. Furthermore, the relationship between the two Testaments is a major interest in the task of doing biblical theology—and you know we care about that task here at this site.
Have you ever read Augustine’s famous statement about how the Old and New Testaments connect? He said, “The New is in the Old concealed; the Old is in the New revealed” (Questions on the Heptateuch, 2.73).
Augustine’s words concisely describe what Christians call “the unity” of Scripture and its “progressive revelation.”
The Old Testament contains prophecies and patterns of Christ. It contains the mystery of the church and the plan of God to bring the nations to salvation through the work of his Son. In other words, the Old Testament conceals the New.