Why do legalism and works-based salvation contradict the Gospel?

Legalism and works-based salvation directly undermine the Gospel message, which proclaims that salvation is a gift of grace through faith in Jesus Christ alone. As seen in Galatians, Paul vehemently opposes the false teachers who insisted that Christians must adhere to Jewish laws for salvation, arguing that such beliefs lead people away from the truth of the Gospel. If salvation were based on works, it would imply that Christ's sacrifice was insufficient, thereby robbing believers of the assurance and joy that comes from knowing they are fully accepted and secure in Him. The true Gospel liberates us from the bondage of performance and invites us into a relationship rooted in grace.