Most Christians at some time or another have wondered what we do with the Old Testament (OT). I don’t think I can answer all the questions. But I want to suggest a way of thinking about the OT that may lead to fruitful exegesis. Before my suggestion, I have two thoughts.
First, as Christians we are called to be a nation before God (1 Peter). We are his people hand he is our God (2 Cor 6). Since we are these things, we are literally God’s kingdom even though we do not have a land.
Second, the argument over the relationship between Israel and the Church is misguided. We focus on ethnicity (Dispensationalism) or religious bodies (Coventalism). But neither of these view strikes at the heart of issue. The principal difference is that of national Covenants. There is an Old Covenant which created a nation before God and a New Covenant which is creating a nation before God. Just like the Old Covenant established a nation, so does the New Covenant.
The Old Covenant, then, is our previous national history. While it has been superseded by the New, it still has relevance as our history. Here, then, is my theory: we ought to view the Pentateuch not as a religious instruction but as a national history. It’s not merely rules for moral conduct. But a national law code.
How do we relate to it? First, our relationship to it is similar to an American’s relationship to the constitution. In the US constitution today, there remains the infamous three-fifths clause (Article 1, Section 2, Clause 3). This phrase is still retained despite it being overturned by the later 14th amendment (Section 2). Why? One reason I surmise is to keep us aware of the past and to help us remember why we changed things. It gives us the context for the significance of the later decision. In a similar way, we Christians retain the OT not because it is binding on us at all. Rather, it gives us the necessary context for the significance of our New Covenant.
Second, the whole OT provides us with the volkgeist (the spirit of the people) of our nation. It connects us to the antiquity of our people and gives us the thought processes by which we should live. We don’t look for absolutes in the law, but rather modes of thought that embody the intention of God. Since this volkgeist comes from God, it is the authoritative way and spirit for our lives.
In sum, the OT is our heritage. It (with the NT) provides us with our national identity. It informs us of who we are and points to where we are going.