Already in the second century, the arch-heretic Marcion pressed this question and came to the conclusion that the Old Testament offered almost nothing to Christianity. He was excommunicated for his views. In the 20th century, the Nazis enacted a remarkably successful elimination of the Old Testament from Christian faith and countless “German Christians” followed suit—to horrific ends. In more recent days, preachers from micro-congregations to multi-campus megachurches struggle with what to do with the Old Testament. Many do their best, many less than that. Some see no way forward but to “unhitch” the two testaments of the Christian Bible.
All of this difficulty with the Old Testament is unfortunate because every page of the New Testament depends on it—extensively, almost exclusively. The very first verse of Matthew is a case in point: “The book of the genealogy of Jesus Christ, the son of David, the son of Abraham” (ESV). Without the Old Testament, readers have no clue what “Christ” means, who David and Abraham are, or how all these figures are related. The original text is even more suggestive: “The book of the genealogy” is biblos geneses in Greek—a rather obvious allusion back to the Book of Genesis.
But the New Testament’s dependence on the Old goes beyond mere information—in some passages, the New Testament suggests that the Old Testament is fully sufficient all by itself for a saving knowledge of God. Consider Jesus’ parable about the rich man and Lazarus (Luke 16:19-31), where Abraham informs the rich man that no one will be sent back from the dead to warn his wayward brothers because, “If they do not listen to Moses and the Prophets, they will not be convinced even if someone rises from the dead” (v. 31).
Texts like Matthew 1 or Luke 16 are everywhere in the New Testament and no doubt give rise to well-meaning statements like: “You can’t understand the New Testament without the Old Testament,” or, per the adage from St. Augustine: “In the Old Testament the New lies concealed, in the New Testament the Old is revealed.” There is nothing wrong with such truisms, but they seem mostly ineffective in completely solving the problem because, in point of fact, many Christians continue to wonder about the Old Testament in a way that they simply don’t (and never will) about the New Testament. And so the question remains: “What does the Old Testament offer to Christianity today?”
My own answer is: Much. Maybe everything.
There are at least four significant gifts the Old Testament offers to Christian faith. If these gifts are not unique to the Old Testament, they are nevertheless far more present in the Old than in the New, and so constitute precious aspects of the whole counsel of God.