What does the Bible say about sealing by the Holy Spirit?

In Ephesians 1:13-14, Paul explains that after hearing the gospel of salvation and believing in Christ, believers are sealed with the Holy Spirit. This sealing serves as a divine authentication of their faith and signifies their belonging to God. The sealing of the Holy Spirit is God's promise, ensuring that believers are His possession until the full redemption is realized. It not only confirms the authenticity of their faith but also indicates their security and assurance in salvation.