We know that the Old Testament is summed up by “love God and love your neighbor” (Matthew 22:36-40). The “new commandment” given by Christ is also summed up by love for God and love for others (John 13:34; 1 John 4:20-21). So we see that both Old and New Testament believers have a law whose foundation is “love God and love your neighbor.” We would expect there to be a LOT of similarity and overlap between these two sets of rules when the moral foundation of love is the defining factor for both. In fact, in one of our lessons we will show that even before the Ten Commandments were given to Moses, the people who followed God already knew them. They didn’t know them as “the Ten” but they knew it was wrong to murder, steal, worship idols, etc. In that sense, the Ten Commandments weren’t “new.” They were simply encoded in a specific and new form and established as Israel’s new law code by a formal covenant at Sinai through Moses.
Consider this illustration. Building and electrical codes might vary from one state to the next. Perhaps the required spacing of outlets or the depth for a foundation might be different. But underneath those different laws is a universal principle—construction must be safe and stable. Whatever is determined to be necessary for a building to be safe and stable becomes the law in that state. Similarly, love for God and love for neighbor is the universal principle. How that is required to be lived out and expressed varies at different times for different people—even people following the same God.
This actually helps explain why the Old Testament law has so many nitty-gritty specifics about cultural practices in the ancient world. God was defining how the specific culture of the Israelites was to set them apart as God’s special people in the world. Now that God’s people are not defined in any way by location, ethnicity, or culture, the New Testament gives only broad moral principles and expects us to figure out how we are to live that out in our location and culture. The New Testament now becomes a law that can be universally learned and applied anywhere by all of God’s people—regardless of culture and ethnicity.
So, while we have a totally “new” testament law, there is still the question of how to understand what we are to do with the Old Testament law.