Law, these verses are clearly law. Jesus not only reminds us of the law given to Moses in the ten commandments, specifically about murder, adultery and swearing oaths, but he carries the commands one step further, bringing the intent of the law to the forefront. He does this to show the Pharisees, and us modern day Pharisees, that none of us are free from sin. We have all sinned. There is no one who has not broken the commandments of God. The Jews and especially the Pharisees, who may have been able to say they did not break the letter of the law, could not say they did not break the law in their heats. Neither can we.
The verse immediately preceding this text, Matthew 5:20, says: “For I tell you, unless your righteousness exceeds that of the scribes and the Pharisees, you will never enter the kingdom of heaven.” In many other places the bible tells us that no one is righteous, no not one.
It is clear here that the intent of these verses is to level the field and remind every person that they are a sinner and as such no better than any other person, even the most vile of sinners. Jesus wants to let us all know that we are sinners in need of saving, unable to get to heaven on our own by our own “good works.”
Law! Who likes the law? Who likes to be told they are sinners? But the truth is that we are all sinners in need of a savior. While it may be more comfortable to preach the Gospel, we are called as pastors to preach the whole council of God, including the unfriendly parts like the law. People may squirm, we should be squirming with them, but preach it we must and allow the law to do its work.
However, we must also offer hope. To preach the law alone is not enough, we must offer hope. The hope here comes in the preceding section in verse 17 where Jesus says he came not to abolish the law but to fulfill it. Jesus did what we cannot do: he fulfilled the law perfectly. He who was born with no sin, lived a sinless life and fulfilled the law in our (my) place. In the verses following this, Jesus tells us to love our enemies. Again, this may be law in that we are commanded or at least called to love our enemies, but there is gospel here in that it reminds us of the One who loved His enemies enough to leave heaven and die for them (Romans 5:6-11).
He who loved us enough to die for us also promises that if we believe in Him, we will be forgiven. Not only that, but He will then live in us and through the Holy Spirit that He sends into us, will live the life we are called to but cannot live on our own (Gal. 2:20). This is the good news, that through faith, we die to sin and Christ lives in us. We still cannot live a sinless life, but Christ who overcame sin, lives in us.