Christians live in the age of promise and grace.  In the first chapter of his gospel narrative, John writes: "the law was given through Moses, but grace and truth came through Jesus Christ."  (John 1:17,  NKJV)

Paul the Apostle writes more about the grace and law than anyone else in Scripture.  As Pharisee, he was perhaps uniquely qualified (being specially prepared by God) to describe the place of the Law in first century Jewish life, as well as from the view of the Scriptures themselves.  Paul knew all about the Laws of Moses.  He also knew how powerfully God had worked in Jesus Christ to finally fulfill all the Law and the prophets.

Jesus did not simply fulfill the predictions made in the Books of the Law about a Savior and messiah.  He also fulfilled all the righteous requirements of the Law.  He lived as we should also live, in honest sincerity and obedient faith before God and men.  Paul says that Jesus did this in order to bring us back to God.  On the cross, Paul says, Jesus Christ became sin for us so that we could become the righteousness of God in Him.