How do we know righteousness is achieved through faith in Christ?

In 1 Corinthians 1:30, we learn that 'of Him, you are in Christ Jesus, who became for us wisdom from God—and righteousness and sanctification and redemption.' This indicates that true righteousness does not stem from our works or efforts but from our union with Christ. Historic Reformed theology emphasizes that God's grace enables us to be counted as righteous. Through His death and resurrection, Jesus fulfilled the law perfectly, granting us His righteousness when we place our faith in Him. Thus, those in Christ are seen as righteous before God, not based on their merit, but on Christ's complete work.