Why must Christians avoid legalism?

Legalism involves adding human efforts or rituals to the grace of God as a means of justification. In Galatians 5:4, Paul warns that attempting to be justified by the law alienates us from Christ and nullifies the grace of God. Legalism can lead to a prideful attitude that seeks to gain righteousness through personal merit, which flies in the face of the gospel that states we are justified by faith alone (Romans 5:1). Additionally, it imposes burdens on others that Christ intended to lift, contradicting the freedom He purchased for us. Therefore, Christians are called to embrace the fullness of Christ's grace and reject any teaching that adds to His completed work.