Now we begin a new paragraph (in the NASB). It is a pivotal section of enormous importance, an introduction to much of what Christ will say in the remainder of His sermon.
Do not think that I came to abolish the Law or the Prophets; I did not come to abolish but to fulfill. For truly I say to you, until heaven and earth pass away, not the smallest letter or stroke shall pass from the Law until all is accomplished. Whoever then annuls one of the least of these commandments, and teaches others to do the same, shall be called least in the kingdom of heaven; but whoever keeps and teaches them, he shall be called great in the kingdom of heaven. For I say to you that unless your righteousness surpasses that of the scribes and Pharisees, you will not enter the kingdom of heaven (Matt. 5:17-20).
If Jesus warned His audience against thinking that He was abolishing the Law or the Prophets, then we can safely conclude that at least some in His audience were making that assumption. Why they were making such an assumption we can only guess. Perhaps it was Jesus’ stern rebukes of the legalistic scribes and Pharisees that tempted some to think He was abolishing the Law and Prophets.
Regardless, Jesus clearly wanted His disciples to realize the error of such an assumption. He was the divine inspirer of the entire Old Testament, so certainly He was not going to abolish everything He’d said through Moses and the Prophets. On the contrary, He would, as He said, fulfill the Law and Prophets.
Exactly how would He fulfill the Law and Prophets? Some think that Jesus was talking only about fulfilling the messianic predictions. Although Jesus certainly did (or will yet) fulfill every messianic prediction, that is not entirely what He had in mind. Clearly, the context indicates He was also talking about all that was written in the Law and Prophets, down to “smallest letter or stroke” (v. 18) of the Law, and to the “least of” (v. 19) the commandments.
Others suppose Jesus meant that He would fulfill the Law by fulfilling its requirements on our behalf through His obedient life and sacrificial death (see Rom. 8:4). But that, as the context also reveals, is not what He had in mind. In the verses that follow, Jesus mentioned nothing about His life or death as being a reference point for the fulfilling of the Law. Rather, in the very next sentence, He stated that the Law would be relevant at least until “heaven and earth pass away” and “all is accomplished,” reference points far after His death on the cross. He then declared that people’s attitudes toward the Law would even affect their status in heaven (v. 19), and that people must obey the Law even better than the scribes or Pharisees or they will not enter heaven (v. 20).
Obviously, besides just fulfilling the messianic prophecies, types and shadows of the Law, and the requirements of the Law on our behalf, Jesus was also thinking about people keeping the commandments of the Law and doing what the Prophets said. In one sense, Jesus would fulfill the Law by revealing God’s true and original intent in it, fully endorsing and explaining it, and completing what was lacking in peoples’ understanding of it. The Greek word translated fulfill in verse 17 is also translated in the New Testament as complete, finish, fill, and fully carry out. That is exactly what Jesus was about to do, beginning just four sentences later.
No, Jesus did not come to abolish the Law and Prophets, but to fulfill them, that is, “fill them to the full.” When I teach this portion of the Sermon on the Mount, I often show everyone a half-full glass of water to serve as an example of the revelation God gave in the Law and Prophets. Jesus did not come to abolish the Law and Prophets (as I say this, I act as though I’m going to throw the half-full glass away); He would fulfill the Law and Prophets (at which time I take a bottle of water and fill the glass to the brim). That helps people understand what Jesus meant.
Concerning the commandments found in the Law and Prophets, Jesus couldn’t have made His point more forcefully. He expected His disciples to obey them. They were as important as ever. In fact, how they esteemed the commandments would determine how they would be esteemed in heaven: “Whoever then annuls one of the least of these commandments, and so teaches others, shall be called least in the kingdom of heaven; but whoever keeps and teaches them, he shall be called great in the kingdom of heaven” (5:19).
Then we come to verse 20: “For I say to you, that unless your righteousness surpasses that of the scribes and Pharisees, you shall not enter the kingdom of heaven.”
Notice that this is not a new thought, but a concluding statement that is connected with previous verses by the conjunction for. How important is keeping the commandments? One must keep them better than the scribes and Pharisees in order to enter the kingdom of heaven. Again we see Jesus was keeping with His theme—Only the holy will inherit God’s kingdom.
Less he contradict Christ, the disciple-making minister would never assure anyone of possessing salvation whose righteousness did not surpass that of the scribes and Pharisees.
 This would be true of what is often referred to as the “ceremonial aspects of the Law” as well as the “moral aspects of the Law,” although much of His fuller explanation concerning the ceremonial law would be given by His Holy Spirit to the apostles after His resurrection. We now understand why there is no need to sacrifice animals under the new covenant, because Jesus was the Lamb of God. Neither do we follow the old covenant dietary laws because Jesus declared all foods to be clean (see Mark 7:19). We don’t need the intercession of an earthly high priest because Jesus is now our High Priest, and so on. Unlike the ceremonial law, however, no part of the moral law was ever annulled or altered by anything Jesus did or said, before of after His death and resurrection. Rather, Jesus expounded upon and endorsed God’s moral law, as did the apostles by the inspiration of the Spirit after His resurrection.