In Jesus’ day the phrase Law and Prophets was shorthand for their Bible which we call the Old Testament. The Law included Genesis-Deuteronomy. The prophets included the historical books (Joshua-Esther) and the prophets as we know them (Isaiah-Malachi). What is not included specifically in that phrase are the wisdom and poetry books. There are a couple of instances where Jesus uses this phrase and once where he adds in the Psalms (Luke 24:44) to reference their authoritative scriptures. Jesus uses this phrase in the sermon on the mount twice and together this phrase bookends the main body of teaching found in the sermon on the mount.
Matthew 5:17 – ““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.”
Jesus spends the better part of three chapters showing what it means to fulfill the Law and the Prophets by clarifying or specifying the original intention or end goal of what the Law and the Prophets were all about and where they were supposed to point anyway (see Micah 6:6-8). Then he concludes this section with the mirror image bookend from 5:17 saying things have now been summed up sufficiently in what was just said in the sermon.
Matthew 7:12 – “ So in everything, do to others what you would have them do to you, for this sums up the Law and the Prophets.”
We miss these big picture structural components in scripture when we break things up and study them in pieces rather than study things as they whole in which they were originally packaged.
You have most likely heard of the golden rule. You may not have known it was in the sermon on the mount and you may not have known that it is placed in a very particular spot in the sermon. The golden rule wraps up Jesus showing us what the Old Testament looks like when it is brought to its intended goal. In between these two book ends, Jesus deals with all sorts of issues that the Law and the Prophets dealt with and redefines them to a more explicit kingdom value system. It is not that Jesus is doing something the Law never intended to do. Jesus is taking the Law directly where it was intended to go the whole time.
What is more, no one else taught this way. This is an authoritative teaching on a re purposing of their sacred scriptures. Imagine if you heard someone do that today how offended you might be by it. The people noticed this difference between Jesus’ teaching and the scribes of his day. We see that in Mark 1:27 where the people say, “The people were all so amazed that they asked each other, ‘What is this? A new teaching—and with authority!'” Some who noticed were not so pleased at this and wanted to kill Jesus for saying such things. We get one example of that in Luke 4 where Jesus reads from Isaiah and tells those in the synagogue that He is the very fulfillment of those scriptures. At first the people were pleased with what he said, “All spoke well of him and were amazed at the gracious words that came from his lips. “Isn’t this Joseph’s son?” they asked.” (4:22). As Jesus continued teaching he crossed enough lines that they decided maybe we wasn’t as kosher as they thought (see Luke 4:24-27) and they tried to throw him over a cliff.
All of that was quite unnecessary when understood properly. When one has eyes to see and ears to hear what Jesus is doing it makes perfect sense. Jesus is doing what the Law in its original form was unable to do and so the Law wasn’t an end to itself. The Law needed to be fulfilled in order for God’s covenant promises to be made good on. It is far easier to pick up on these things reading back into the Law and the Prophets than reading them prior to Jesus or even during Jesus’ ministry (remember, even the disciples had a hard time “getting it”). But it was still there. God told them these things would happen. He told them there would be a prophet like Moses to come in Deuteronomy 18 and about a future circumcision not of the flesh but of the heart in Deuteronomy 30 . He told them he would establish a new covenant with his people in Jeremiah 31. He told them the seed of Abraham wouldn’t just be a blessing to Abraham’s descendants but to all nations in Genesis 12, 15 & 17. He told them about the future fulfillment and restoration of all things in Isaiah 60-65. Jesus is fulfilling what God said would be fulfilled. It is something new and something better but it was not something unexpected.