In whom you also trusted, after that you heard the word of truth, the gospel of your salvation: in whom also after that you believed…
What is this seal? It is a signet, or a signet ring, used by kings and others, for various important ends, some of which we shall now mention.
1. The seal was attached to letters to give them the royal authority; and so the Church is the epistle of Christ, known and read by all men (2 Corinthians 3:3). The gifts and Daces of the Holy Spirit are the seal of God upon this epistle of His mercy, where the nations of the world and the angels of heaven may read His manifold wisdom (Ephesians 3:10).
2. The seal is used to secure the possession of property (Romans 15:28), and to show that it belongs to a particular master and no other. It has His seal. Jesus Christ has purchased His people with His own precious blood, and the sealing of the Spirit is the mark that they belong to Him.
3. As the seal is the conclusion of the letter or the agreement, so it signifies often the last, the end, the perfection; thus the Moslems call Mohammed the seal of the prophets, viz., the last and most glorious of them. In this respect also the sealing of the Spirit is full of meaning. He is the last of the heavenly witnesses, and to blaspheme Him is certain destruction.
(W. Graham, D. D.)
Parallel VersesKJV: In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise,