Recently I have heard it said that if you allow the New Testament to interpret the Old Testament you are committing a hermeneutical error. Frankly I do not understand how anyone who has read the New Testament more than once could say that, nevertheless the idea continues to float around the theological world. From my perspective, the New Testament insists that we read the Old Testament in its light and our commitment to Jesus as Lord demands the same thing. For instance, when Jesus says that he did not come to abolish the law and the prophets but to fulfill them (Matthew 5:17), he is claiming Lordship over the Old Testament and telling us that any exposition of the Old Testament that does not interpret the text in light of him is deficient.
This same point is made throughout the New Testament in different ways, but perhaps it is never more clearly and forcefully propounded as in the letter to the Hebrews. The unknown but inspired writer of Hebrews shows us how to read the Old Testament. He reads the text with great care and skillfully connects the theological "dots" that lead us to Jesus and the fulfillment of God's salvific purposes in him. One passage that I recently shared with my seminary Hebrews class is Jeremiah 31:31-34, which is quoted at length in Hebrews 8. It is part of a section of Hebrews in which the author is demonstrating that we have in Jesus the ultimate great high priest who serves in the heavenly sanctuary, the true tabernacle, set up by the Lord, and not by mere human beings. In this passage, he goes so far as to say that the earthly sanctuary was only a copy and shadow of what is in heaven. In other words, the tabernacle and the Levitical priesthood attached to it has no meaning apart from what it temporarily symbolized as God revealed his way of salvation in human history. Then the writer goes on to tell us that this not only applies to the earthly tabernacle, but to the first or Sinaitic covenant (which is not the "covenant of works" but the covenant made with Israel at Sinai). There was something wrong with this covenant because it could not bring the people near to God. It served a purpose in the plan of God for a period of time, but now that Jesus Christ has come, it is obsolete and outdated and has been replaced by a new and better covenant of which Jesus is the guarantor and mediator.
From the development of his argument it is clear that the writer does not believe that the Old Testament has a meaning for Israel that it does not have for the church. If he did, he could not appeal to this passage in support of the new covenant which brings together both Jewish and Gentiles believers in the church of the Lord Jesus Christ. Without apology, or explanation, he applies Jeremiah 31:31-34 to Christian believers which indicates that he understands "Israel and Judah", to whom the words are addressed, to refer to the spiritual nation which is the fulfillment of the promises made to Abraham. Failure to read Jeremiah in this way will result in a failure to understand what he is talking about. Jeremiah 31:31-34 is about the new covenant that is the result of the superior ministry of Jesus and established on better promises. Any other interpretation of the passage is sub-Christian at best, and at worst, represents a sinful and stubborn refusal to honor and glorify Jesus as the great high priest who has sat down at the right hand of the throne of the Majesty in heaven. This is the hermeneutical error we must studiously avoid no matter what our theological tradition.