How does the Holy Spirit seal us? What is the seal of the Holy Spirit?

from the old testament

• In places like Ezekiel 9:4, God commands a mark to be placed on those who belong to Him, protecting them from judgment. This points to the Spirit’s seal as God’s mark that we are His.
• Circumcision (Genesis 17:10–11) and the Sabbath (Exodus 31:13) were visible signs of belonging to God’s covenant people. These outward signs foreshadow the inward seal of the Spirit that marks us as God’s in Christ.
• In the Old Testament, the Spirit would come upon individuals like David (1 Samuel 16:13) to set them apart for God’s purposes. Now that Jesus died, rose again, and ascended to heaven, the Holy Spirit seals believers permanently—setting us apart as God’s possession, secured for His plans.

from the new testament

• In biblical times, a seal was a guarantee. Ephesians 1:13-14 shares regarding the Holy Spirit, "In him you also, when you heard the word of truth, the gospel of your salvation, and believed in him, were sealed with the promised Holy Spirit, who is the guarantee of our inheritance until we acquire possession of it, to the praise of his glory." According to this passage, the seal of the Holy Spirit takes place at the point of salvation. It is a promise or guarantee of the Christian's future, eternal inheritance with Jesus Christ.
• The Greek word translated as "seal" is shragizo, which means "to set a seal upon, mark with a seal." A seal could be used to guarantee a document or letter (see Esther 3:12), indicate ownership (see Song of Songs 8:6), or protect against tampering (Matthew 27:66; Revelation 5:1). The Holy Spirit is our seal in every sense of this word.
• The seal of the Holy Spirit in the believer's life helps to guarantee he or she is a child of God. Romans 8:16 shares, "The Spirit himself bears witness with our spirit that we are children of God."
• The seal of the Holy Spirit serves as a mark that we truly belong to Christ. Romans 8:9-10 teaches, "You, however, are not in the flesh but in the Spirit, if in fact the Spirit of God dwells in you. Anyone who does not have the Spirit of Christ does not belong to him. But if Christ is in you, although the body is dead because of sin, the Spirit is life because of righteousness." First Corinthians 6:19-20 also notes, "Or do you not know that your body is a temple of the Holy Spirit within you, whom you have from God? You are not your own, for you were bought with a price. So glorify God in your body."
• The seal of the Holy Spirit helps protect against tampering or attack. Romans 8:13 declares, "For if you live according to the flesh you will die, but if by the Spirit you put to death the deeds of the body, you will live." In a very real sense, God's Spirit protects us and guarantees our eternity with the Lord.

implications for today

At what point does the sealing of the Holy Spirit take place? It takes place when a person believes the gospel (Ephesians 1:13; John 7:37-39). At that point, God's seal offers the promise of eternal life (John 3:16) because of salvation based on God's grace through faith in Jesus Christ (Ephesians 2:8-9).

The seal of the Holy Spirit offers a wonderful glimpse of God's role in salvation. When we receive salvation in Christ, we are given a guarantee, exchange our ownership for His, and are protected against forces of evil. This seal should provide wonderful encouragement for the believer against the spiritual battles in this life (Ephesians 6:12) and anticipation for the life to come.