We all have been blessed. That is not salvation, by itself.
we were sealed by the Holy Spirit of promise when we believed. Not going to be. Were. A seal cannot broken, except by the recipient, Jesus Christ. The redemption of the purchased possession. Not going to be. Have been. (BTW, that's eternal security).
Let us examine what a seal meant in Biblical times. http://www.bible-history.com/eastons/S/Seal/ says that:
"Seal commonly a ring engraved with some device (Gen. 38:18, 25). Jezebel "wrote letters in Ahab's name, and sealed them with his seal" (1 Kings 21:8). Seals are frequently mentioned in Jewish history (Deut. 32:34; Neh. 9:38; 10:1; Esther 3:12; Cant. 8:6; Isa. 8:16; Jer. 22:24; 32:44, etc.). Sealing a document was equivalent to the signature of the owner of the seal..." This is saying that the OT seal was a signature, not a ziplock baggie. To continue:
"When God is said to have sealed the Redeemer, the meaning is, that he has attested his divine mission (John 6:27). Circumcision is a seal, an attestation of the covenant (Rom. 4:11). Believers are sealed with the Spirit, as God's mark put upon them (Eph. 1:13; 4:30). Converts are by Paul styled the seal of his apostleship, i.e., they are its attestation (1 Cor. 9:2). Seals and sealing are frequently mentioned in the book of Revelation (5:1; 6:1; 7:3; 10:4; 22:10)."
Again, the use of 'seal' here is meant to be a mark or signature, and not a ziplock baggie. The use of the term 'seal' in Matthew 27:66 would have been an indicator of the position of the rock only, since a guard was set over tomb.
So what does 'seal' mean to us? It is a sign of God's promise to us. God does not break His promises, but man can and does. Therefore, when man does, then Paul tells us:
Romans 2: 5 By your stubbornness and impenitent heart, you are storing up wrath for yourself for the day of wrath and revelation of the just judgment of God, 6 who will repay everyone according to his works: 3 7 eternal life to those who seek glory, honor, and immortality through perseverance in good works, 8 but wrath and fury to those who selfishly disobey the truth and obey wickedness. 9 Yes, affliction and distress will come upon every human being who does evil, Jew first and then Greek. 10 But there will be glory, honor, and peace for everyone who does good, Jew first and then Greek.
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.Eph 4:30 — And grieve not the holy Spirit of God, whereby ye are sealed unto the day of redemption.
2Cr 1:20 — For all the promises of God in him [are] yea, and in him Amen, unto the glory of God by us.
2Cr 1:21 — Now he which stablisheth us with you in Christ, and hath anointed us, [is] God;
2Cr 1:22 — Who hath also sealed us, and given the earnest of the Spirit in our hearts.
Seal =sphragizō
to set a seal upon, mark with a seal, to seal a) for security: from Satan
b) since things sealed up are concealed (as the contents of a letter), to hide, keep in silence, keep secret
c) in order to mark a person or a thing
1) to set a mark upon by the impress of a seal or a stamp
2) angels are said to be sealed by God
d) in order to prove, confirm, or attest a thing
1) to confirm authenticate, place beyond doubt
a) of a written document
b) to prove one's testimony to a person that he is what he professes to be