What does the Bible say about mixing grace and works?

In Galatians, Paul warns against false teachers who sought to mix grace with works, declaring that such an act nullifies the grace of God. He emphasizes that adding any requirement, such as circumcision or adherence to the Mosaic law, to the gospel of grace means one is attempting to earn salvation, which is impossible since all have sinned. True salvation is solely through Christ and cannot be attained through human effort; any attempt to do so is described as a perversion of the true gospel. This principle highlights the importance of relying on Christ’s sacrifice, reminding believers that the true gospel must remain untarnished by works.