“Knowing that a man is not justified by the works of the law, but by the faith of Jesus Christ, even we have believed in Jesus Christ, that we might be justified by the faith of Christ, and not by the works of the law: for by the works of the law shall no flesh be justified. “
Andrew Wommack in his Bible commentary explains what is meant by the the term, "works of the law"
What are "works of the law"?
Any rule, command or law that a person observes in an attempt to be accepted in right standing with God is a "work of the law." In other words, "works of the law" are a righteousness produced by one's self, a righteousness belonging to one's self, offered to God as a means of meeting God's standard for acceptance. Philippians 3:9 says it's ". . .having MINE OWN RIGHTEOUSNESS (a righteousness belonging to me) which is of the law. . .".
"Works of the law" have always been man's attempt to be accepted by God. Paul says, Let me "be found in Him not having a righteousness of my own that comes from the law, but that which is through faith in Christ-the righteousness that comes from God and is by faith" (Phil.3:9-NIV).
It takes a radical revelation of the gospel of grace to abandon faith in the works of the law. God's standard of righteousness is the RIGHTEOUSNESS OF GOD alone.