The sealing of the Spirit is the work by which God marks believers as His own and secures them unto the day of redemption, the Holy Spirit Himself being the seal stamped upon them. Paul declares that in Christ, after they believed, the Ephesians “were sealed with that holy Spirit of promise,” and warns them to “grieve not the holy Spirit of God, whereby ye are sealed unto the day of redemption.” A seal in the ancient world served several functions, all of which illumine the doctrine. It marked ownership, as a master stamped his property: the believer, sealed with the Spirit, bears the mark that he belongs to God, who knows them that are His. It signified authentication and approval, as a royal seal authenticated a document: the indwelling Spirit is God’s authenticating mark that the believer’s faith is genuine. And it guaranteed security and preservation, as a sealed document was protected and a sealed tomb made fast: the sealed believer is kept safe, preserved unto the day of final redemption, the Spirit being the divine guarantee that he will not be lost. The seal is thus closely joined to the doctrine of the Spirit as the earnest or down-payment of the inheritance and to the perseverance of the saints. It is the same Spirit who indwells, the indwelling itself constituting the seal—not a separate later experience, but the abiding presence of the Holy Ghost in every true believer, the inward witness and divine assurance that he is owned, approved, and kept by God.