For I say unto you, That except your righteousness shall exceed the righteousness of the scribes and Pharisees, ye shall in no case enter into the kingdom of heaven.Matthew 5:20
In the next section of His sermon, Jesus is going to correct many of the doctrinal errors the Scribes and Pharisees have taught the people for several generations. However, we must understand His purpose in correcting these errors. Jesus is not saying we need to go back to the law and follow it better than the Pharisees.
Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law is the knowledge of sin.Romans 3:20
God never intended the law to be used as a way to gain access to heaven. Jesus teaches the proper interpretation of the law so that the people of God can properly live out their practical sanctification day by day.
Our own righteousness is no better than that of the Scribes and Pharisees. We need something much greater to justify us before a Holy God.
So how can anyone enter into heaven? That is the very question that Jesus answers in His conversation with Nicodemus. As recorded in John Chapter 3, Jesus says that a man must be born again in order to see or enter into the kingdom of heaven. There must be a fundamental change from the inside, not just an outward conformity to the law, in order to stand in the presence of a Holy God.
We learned previously that we are judged righteous based on the imputed righteousness of Jesus Christ. This declaration of righteousness states that we are not guilty of sin. However, the possibility of sin still exists in our bodies. The new birth begins a change in us that will ultimately be completed in the resurrection. This change moves us toward a time where not only are we not guilty of sin, we are no longer capable of it!
And let us not forget, this new birth is much like our natural birth in that we have no control. It is done by the sovereign and irresistible power of the grace of God.
The wind bloweth where it listeth, and thou hearest the sound thereof, but canst not tell whence it cometh, and whither it goeth: so is every one that is born of the Spirit.John 3:8