Why is Christ's sacrifice not in vain?

The question posed in Galatians 2:21—'Is Christ dead in vain?'—is a profound one that emphasizes the significance of Christ's atoning work. If righteousness could be obtained through the law, then indeed, Christ's sacrifice would be futile. However, Paul emphatically affirms that Christ is 'the end of the law for righteousness to everyone that believeth' (Romans 10:4). His self-giving love and sacrifice satisfy divine justice, making believers righteous before God based on faith rather than legal observance. Thus, His death fulfills the promise of salvation, ensuring that His work was indeed not in vain.