I believe this is the key verse for the Sermon on the Mount. It contains the central idea, or view, for the entire sermon. A large portion of the sermon, especially from this point on, is a development of what true righteousness is in the kingdom of heaven, as opposed to righteousness under the Law of Moses and the Pharisees’ interpretation thereof.
The primary difference that will be seen in the following verses is that the Law of Moses regulated civil conduct and dealt with obvious actions of an individual, while the laws of the kingdom of Christ are given to the individual to regulate their inner spiritual condition and motives of conduct.
Jesus declared that a person’s righteousness must exceed the righteousness of the Scribes and Pharisees if they hope to go to heaven, Matthew 3:7 / Luke 18:9-14.
Coffman, in his commentary, says the following.
‘The religion of the Pharisees, hence their righteousness, consisted of externals, ceremonials, rituals, liturgies, and formalities of many kinds, with little or no attention being paid to the condition of the heart. Christ flatly denounced such a concept and indicated that no one could be saved in such a state as that of the typical Pharisee of his day.’
The righteousness of the religious leaders was outward only, Isaiah 64:6 / Matthew 23:13-33, but Jesus’ disciples must have spiritual righteousness that grows out of love for God and for man.
It must not be self-righteousness or ceremonial righteousness but true moral righteousness, a righteousness that is genuine both privately and publicly, Luke 18:9-14.