In the good, old days, men used to place a seal on their documents before sending them off. The seal was usually made of clay or stone with a specific identifying mark carved into the face, which was then pressed into melted wax. When the document arrived at its destination, the seal proclaimed who sent it and authenticated the document.
We, too, are sealed, but not by mere wax, which is easily destroyed. “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, with a view to the redemption of God’s own possession, to the praise of His glory” (Ephesians 1:13-14, NASB). The word translated “sealed” is from the Greek word σφραγιζω (sphragizo), meaning “to stamp (with a signet or private mark) for security or preservation” (AMG’s Annotated Strong’s Greek Dictionary of the New Testament).
When you believe, when you repent of your sins and turn your heart to Jesus, you become identified as one of His own! The Spirit, which you are sealed with at the moment of salvation, is God’s guarantee that He has purchased you, bought you with His blood.
When you are sealed with the Holy Spirit of promise, it means there is now “nothing incomplete or defective about you. When God made you new, the last thing He did was check you out, thoroughly examining and inspecting you before placing His final seal of approval on your heart” (Rick Renner, Sparkling Gems from the Greek).
Once you are sealed with His Spirit, you are sealed for eternity! You are His and nothing can ever melt His seal off of you. 🙂