How do we know that believers are sealed by the Holy Spirit?

The sealing of believers by the Holy Spirit is a significant theme in the New Testament, referring to God's ownership and the assurance of salvation. Ephesians 1:13-14 states that believers are sealed with the Holy Spirit as a guarantee of their inheritance. This sealing signifies that the purpose God has for a believer cannot be altered, much like a king's seal that assures a decree's permanence. Thus, believers can have confidence that their salvation is secure and their future is assured in Christ.