How do we know sanctification is part of salvation?

Sanctification, the process of being made holy, is inseparable from justification in the life of a believer. Paul emphasizes in Galatians that if one believes their sanctification is partly their work, they fall from grace (Galatians 5:4). The Scriptures indicate that true faith will produce the fruit of sanctification as Christ is formed in us (Galatians 4:19). This understanding emphasizes that both justification and sanctification are fully the work of Christ and must be received by faith, aligning with the doctrine of TULIP — particularly the perseverance of the saints.