What is the difference between the old covenant and the new covenant?

THOMAS: One answer would be what John says in his prologue: “The law came by Moses, but grace and truth came by Jesus Christ” (John 1:17). What does John mean? Does he mean there was no grace in the Old Testament? Does he mean there is no law in the New Testament? Obviously not; he is making a relative contrast. I think John Murray said that John is making a relative contrast in absolute terms. There was so much law under the Old Testament that it appears as though the old covenant added laws relative to the state of Israel as an infant and a teenager.

I remember when I first allowed our children to be home alone. My wife was at a Bible study, and I was at home with the children. They were in their early teens, and an emergency happened. I had to go to the hospital. I told my children four hundred things they were not allowed to do until their mother came home, but the number one thing was, “If someone knocks, do not answer the door.” My children are now in their forties. I don’t give them any laws at all, but I do expect them to live in relative obedience to some standards. That’s a way of saying that the old covenant was an administration for teenagers and the new covenant is an administration for adults.

PARSONS: I’m going to add one important thing that took me years to understand. The Old Testament does not equal the old covenant. The old covenant, technically speaking, is the Mosaic covenant. The Mosaic covenant is the law, as Derek was saying and as John makes clear in his prologue.

We did a Tabletalk issue a few years ago titled “What’s So New about the New Covenant?” In that issue, we tried to help people understand what is new and unique about the new covenant, as well as the continuity between the old and new covenants. That is just a point of clarification, but it’s an important one.

GODFREY: It’s important to remember that our theologians have used the word covenant to describe a lot of different relationships. There is not only the old covenant and the new covenant, but there is also the broader framework in Scripture of the covenant of works that was given to Adam, in which he was to maintain his relationship to God with perfect obedience. Then there is the covenant of grace, and both the old covenant and the new covenant are administrations of the covenant of grace.

The Mosaic economy, as an administration of the covenant of grace, has a particularly legal cast. Part of the function of the Mosaic law, as Paul says over and over again, is to teach the reality of sin. It’s difficult to keep all the law of Moses, so it impinges on the people of God to know their sinfulness and their need of mercy.

THOMAS: That function of the Mosaic law is the reason why Paul, in 2 Corinthians, speaks of the old covenant as an administration of death and the new covenant as an administration of glory. It’s a relative contrast in absolute terms, but clearly, one of the aspects of the old covenant was to reinforce our inherited depravity. By maximizing the laws, they revealed sin.