“Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them. For truly, I say to you, until heaven and earth pass away, not an iota, not a dot, will pass from the Law until all is accomplished. Therefore whoever relaxes one of the least of these commandments and teaches others to do the same will be called least in the kingdom of heaven, but whoever does them and teaches them will be called great in the kingdom of heaven. For I tell you, unless your righteousness exceeds that of the scribes and Pharisees, you will never enter the kingdom of heaven.” -Matthew 5:17–20
No doubt this is a hard section of Scripture. The main point is that Jesus Christ is the fulfillment of the Old Testament law and the prophetic statements from the Prophets. Saying that Jesus is the fulfillment of the law does not mean that he came to nullify, loosen, or dissolve the commandments of God. On the contrary, he says that not even the smallest letter from the commandments will pass away until all is either accomplished or fulfilled. He exhorts his listeners (including us) to uphold and teach the commandments of God. He even warns those who might tend to relax the commandments that they will be placed in a lower class in heaven.
So what do we make of this section? When a new teaching comes down the pike, we tend to push aside the old for the new. This was true of Jesus’ time period as well. Jesus wants his listeners to be assured that his teaching is not abolishing what came before him, but rather fulfilling it. He embodies everything the distinctive food and sacrificial laws aimed at. He encapsulates the moral law by his person and life. His teaching is not new in the sense that he is nullifying or replacing old truth. He is rather teaching the heart behind the law and the prophets of old. The law says do not murder. Jesus teaches murder begins as anger in the heart of man. The person who is angry with his brother is equally deserving of hell as the one who kills him.
Jesus also teaches a law of love. He again is not teaching something new, but rather boiling down four-hundred some commandments to two; love the Lord with all your heart, and love your neighbor as yourself. On these two commandments hang all the law and the prophets. If you love your brother, you will not murder him. If you love the Lord, you will seek to obey him.
Jesus’ also fulfilled the promise to take the external law and place it in the heart of man. He takes out the heart of stone, and replaces it with a heart of flesh. He does this through the gospel of free grace. He does this by sending the Holy Spirit to take up residence in the heart of sinful man. The Holy Spirit fulfills in the heart of man what Jesus accomplished for mankind at Calvary.