This is an attempt to understand Jesus’ teaching about the Law in Matthew 5:17-20.
Jesus’ announcement of the arriving kingdom evidently raised questions about the continuing place for the Law. This may have especially been the case if His hearers made the correct connection between the coming kingdom and the New Covenant, a covenant that Jeremiah said would not be like the covenant made at Sinai (Jer. 31:31-32).
Jesus’ clarification has been itself confusing for some interpreters. There are a number of false interpretations that can be cleared away at the outset.
First, when Jesus said that he did not intend to abolish the law, he was not saying that Christians would be obligated to obey every part of the Old Testament law until the end of the world. Hebrews 10:18 has made it clear that Jesus’ death brought an end to the sacrificial system. Jesus himself declared all foods clean, rendering the Old Testament food laws no longer binding on God’s people (Mark 7:19; cf. Acts 10:15). Even within Matthew 5, Jesus is going to make some changes to the Mosaic law (see for instance Jesus’ comments about divorce in light of Matt. 19:8-9).
Second, some people argue that when Jesus says that he is not going to abolish the law, he means the moral law rather than the civil or ceremonial law. But the moral, civil, ceremonial distinction was developed during the Middle Ages. It can’t be read back into the New Testament.
The key to understanding the passage is to understand what Jesus meant by “fulfilling” the law. Matthew uses this term fifteen other times in his gospel and in all but three he is referring to the fulfillment of the Old Testament. In these other passages Jesus doesn’t necessarily fulfill a direct prophetic prediction; but in every case he fulfills the Old Testament by being that to which it pointed forward.
In relation to the Law, Jesus fulfills the Old Testament by bringing about the kingdom in which it is possible to live in the way that the Old Testament pointed toward.
This means that the Old Testament retains its validity until heaven and earth pass away and all is accomplished even though it is no longer the binding covenant of God’s people. Thus one who “looses” an Old Testament commandment comes under God’s disfavor. What God actually demands for entrance into the kingdom of heaven is a righteousness far beyond that of Israel’s most scrupulous law-keepers.