"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

He [Jesus] tells the disciples point blank that their righteousness must be greater than that of the scribes and the Pharisees; otherwise, they should under no conditions enter into the kingdom of Heaven. Even Nicodemus, who skulked in the darkness of night to come unto our Lord, did not understand that simple truth. There is no shred of Scriptural evidence to indicate that death changes the spirit within. Therefore said the Christ, that we must be born from above (to be fit to come in the Presence of God). That is the "greater righteousness" He referred to in Matthew 5:20 which would outshine that of the scribes and the Pharisees. For the latter two categories, no matter how zealously they kept the Law, they did what was right because it was the Law; but when one is born anew from the incorruptible seed (which comes from above), then is he no longer concerned over the Law! He doesn't steal, kill, or commit iniquity because it was so ordained in the Mosaic Law, but he lives in righteousness for the simple reason that the seed of truth and righteousness and good now lives within his own heart, perpetually aspiring unto righteousness. He may err, he may falter, he might even sin, but only because of human weakness and spiritual immaturity. That eternal flame within his heart shall ever mount upward, transforming him from image to image, even into the likeness of Jesus Christ Himself. That life-seed from out of His glorified body is the core. But every seed requires time to grow and flourish. Ultimately, in the process of time, the son stands shoulder to shoulder with his father. But for you and me, that moment is still in the dimly distant future.

Christ's Sermon on the Mount