Ephesians 4:30 And do not grieve the Holy Spirit of God, by whom you were sealed for the day of redemption.
Ephesians 1:13–14 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.
To be sealed means to be made secure. When an envelope is sealed with a melted wax seal it guarantees the contents are preserved for the intended recipient. The Holy Spirit seals us as one of the redeemed ones. We can have the assurance of being preserved for eternity when we are surrendered to His will. This is reason enough we should never want to grieve Him by disregarding His work in our lives. Think about the incredible blessing that is our when we know we are sealed or made secure with the Holy Spirit. Praise God!