What does the Bible mean by progressive sanctification?

Progressive sanctification is the process of spiritual growth whereby believers increasingly reflect the character of Christ in their lives. While justification is a one-time legal declaration of righteousness due to faith in Christ, sanctification is an ongoing work of the Holy Spirit in the believer. As exemplified in Philippians 1:6, where Paul expresses confidence that God 'who began a good work' will carry it on to completion, this reveals that sanctification is both a divine and human endeavor. Believers are called to actively participate in this growth through prayer, study of the Word, and obedience, while also relying on God's grace and strength. Thus, progressive sanctification is essential to the Christian life, as it confirms the authenticity of one's faith and shapes their character for God's glory.