How do we know that self-righteousness is condemned in the Bible?

Self-righteousness is condemned throughout scripture, particularly exemplified in the teachings of Jesus regarding the Pharisees. The Pharisees trusted in their own righteousness, believing that their strict adherence to the law made them justified before God (Luke 18:9). Jesus indicated that unless one's righteousness exceeds that of the Pharisees, they could not enter the kingdom of heaven (Matthew 5:20). This declaration illustrates the inadequacy of legalistic righteousness, which can be merely external.

Moreover, biblical texts such as Romans 3:20 affirm that no one can be justified by works of the law. Paul emphasizes that apart from faith in Christ, all human efforts are like filthy rags (Isaiah 64:6), stressing the need for a righteousness that comes through faith (Philippians 3:9). Thus, self-righteousness is portrayed as an obstacle to understanding true grace and the need for a Savior, revealing the heart's need for God's transformative work.