Why is the seal of God significant for Christians?

The seal of God, as explained in Ephesians 1:13, indicates that believers are marked with the Holy Spirit, which represents God's authority and promise. This seal assures Christians of their salvation and provides a sense of security as they navigate challenges in faith. Just as seals in antiquity denoted ownership and authenticity, the Holy Spirit's presence in believers serves as a reminder that they are God's own possession, purchased through the sacrifice of Christ. This seal also signifies that believers are guaranteed eternal life, reinforcing the idea that God will complete the good work He began in them (Philippians 1:6).