In Him, you also, after listening to the message of truth, the gospel of your salvation-having also believed, you were sealed in Him with the Holy Spirit of promise, who is given as a pledge of our inheritance to the view of redemption of God’s own possession, to the praise of His glory. Ephesians 1:13, 14 (New American Standard Bible)
I spent nearly ten years working in the air freight and trucking (dry goods) industries.
One thing that was necessary when any container or trailer was shipped was not only to be locked but sealed with a numbered security strip. That seal showed the shipment was a deposit of guarantee by our company until the freight was received by the customer.
When we hear and believe we are at that instant ‘sealed’ with the Holy Spirit of promise. Sealing represents security, authentication, approval and identification of ownership. The seal is done in Christ and the Holy Spirit is the instrument of the seal. It is a deposit guaranteeing our own inheritance in God through His Son. But it is more than a pledge as a pledge can be altered or even ignored; the seal of the Spirit is a guarantee of more to come. In essence the deposit of the Holy Spirit is a little bit of heaven with a guarantee of much more that He will give to us in the eons to come.
Because of this, believers acquire every spiritual blessing including election, predestination, adoption, grace, forgiveness, wisdom, understanding, knowledge of the mystery of His will, and inheritance. We remain God’s possession and delight to the praise of His glory. Being sealed by the Holy Spirit is a secure and precious privilege. It is not done by human means but by Christ Jesus as His Ultimate Seal of love and power. In its security and approval we are now and will remain God’s shining glory for eternity.