Greek Exegesis Class was about to begin. I'm one of the old guys there. Less sophisticated and a little less 'with it'. But one of the young and experienced seminary students was talking with his buddy. He knows the system. He says to his buddy, "You don't really need to study the Old Testament, just study the New." He went on to explain that this is where you need to preach from. It is contains our theology and so just concentrate on that.
In a sense we do have to set priorities, we can't be experts on all aspects of Scripture. We do have to concentrate on the passages with foundational significance. But I would argue this is exactly why our churches need more than ever the Old Testament. Our people do not start out with an understanding of how God works in his sovereignty. We don't know how he works in covenant relationships with his people. We don't understand about suffering. We can tell someone how to say the sinners prayer but we don't know who we are saying it.
Stephen in preaching to the Jews at his defense trial just before he was stoned answered his accusers with the Old Testament. (Acts 7) His accusers leveled charges that he was against the customs of Moses and the Temple. He developed his defense from the Old Testament narratives about Abraham, Joseph, Moses and the building of the Temple. Some of his points was that neither Abraham nor Moses worshiped in the Temple, and besides the Temple can not contain God who made heaven and earth. Moses was actually rejected by the people. He pointed to another one who was to come and the Jewish leaders of the day rejected him too.
If the early church developed their message from Abraham, Joseph, and Moses, can we better them?
If we don't understand how Jesus was foretold by Moses and the prophets in the Old Testament, how can we really know the one whom we testify about?
In our American middle class churches we need to understand that Abraham lived a very different lifestyle. If are to be children of Abraham with faith, we have to understand what that means. He wondered in the desert. He left his home. He never possessed the promise land. That was left to his children. He was a man of faith, not of success.