Righteousness is one of the key ideas in the Sermon on the Mount: 

Matthew 5:10 – “Blessed are those who are persecuted for the sake of righteousness.”

Matthew 5:20 – “Unless your righteousness surpasses that of the Pharisees and the teachers of the law, you will never enter the Kingdom of heaven.”  (Followed by a string of teachings about righteousness, specifically having to do with commandments regarding murder, adultery, divorce, oaths, revenge, and loving enemies.)

Matthew 6:1 – “Be careful not to do your ‘acts of righteousness’ before men, to be seen by them.

Matthew 6:33 – “But seek first his kingdom and his righteousness, and all these things will be given to you as well.”

Righteousness is a matter of the heart. 

• Righteousness is not just about behaving the right way.
• Righteousness is also about wanting to live the right way.
• Righteousness is having every fiber of our being tuned to the right ways of God.
• Perhaps the best way of defining righteousness is: to be like Jesus himself.

At some point, we realize that this righteousness is unattainable on our own strength, on our own merit, on our own determination.  We come to Jesus – poor in spirit, mourning over our sins, recognizing our need to submit with meekness to Christ as Lord of our life.   We come, hungering and thirsting for a righteousness that we could never produce in and through ourselves.