Paul reminds his friends in Ephesus that they have the Holy Spirit. This relationship can be described in different ways. Here Paul refers to it as the sealing of the Spirit. What does he have in mind?
It was common at the time Paul wrote for persons to put a seal on property to indicate ownership; a seal was also used to authenticate the genuineness of an object as well as for providing security. By the sealing of the Spirit Paul means that the presence of the Spirit is the identifying mark of genuine discipleship because he never leaves any of his people.
Paul also uses another illustration to depict what it means to have the Spirit. He says that the Spirit is the earnest of our inheritance. He borrows this idea from the language of trade where it describes a down-payment for an object, with the remainder to come at a later date. It is more than a mere pledge or promise because it consisted ‘of a sample of that which afterwards would be paid in full’ (John MacPherson). The difference can be seen in this illustration. Suppose I owe £5 to another person. As a sign that I will repay I give him an object I own such as a book or an ornament. That is a pledge because there is no connection between the book and the money I owe. But if I give the person 50 pence or £1, then I am giving an earnest because the deposit is part of the full payment.
The Spirit as the earnest is also the guarantee to each believer that he or she will receive the fullness of the inheritance, or as Paul calls it here, the purchased possession. But he is a guarantee in kind or in sample, which means that he will bring into their current experience foretastes of eternal blessedness. The Spirit’s work in our lives as believers is a sample of how he will work in us in the eternal world.
‘As days of heaven enjoyed on earth enliven the Christian’s thoughts of heaven, and quicken his desires after meetness for it, while at the same time they deepen the conviction that such an inheritance is in store for him; so the earnest of the inheritance, afforded by the Spirit impressing Himself upon the believer’s heart, intensifies his longings and renders his conceptions more vivid, while it increases his assurance that at last he shall enter upon the full possession of that spiritual inheritance of which he has received a sample’ (John MacPherson).
Heaven is the place where Jesus Christ is central, and it is the goal of the Spirit’s work in believers today to make Jesus central in their lives, to increase their love for him and devotion to him.
So we see from this verse how crucial the Holy Spirit is in the lives of Christians. He is the Source who empowers their Christian living from the start, he is their Strength along the journey, and he is the Sample of the glory that is yet to be. No wonder Paul says in Ephesians 4:30, ’Grieve not the Holy Spirit, by whom you were sealed until the day of redemption.’