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, 14Which is the earnest of our inheritance until the redemption of the purchased possession, unto the praise of his glory. Ephesians 1:13-14
The “earnest” mentioned here bears some similarity to our usage today of the phrase “earnest money” – referring to the money that is often required as a deposit when one enters into a sales contract to buy real estate. It is money that is given to express our sincere, earnest intention to fulfill the terms we’ve agreed upon, guaranteed by the fact that legally one must forfeit their “earnest” money if they fail to follow through with the deal. And so, here too it speaks of a guarantee – but this guarantee is from the faithful, almighty God who cannot fail. So the saved are convinced by God the Holy Spirit of God’s gospel wherein they see all of the requirements for their salvation having been fully met by the doing and dying of their Substitute, with no contribution remaining due from their hand. In other words, their salvation is truly to “the praise of His glory.” And having been so convinced – having this mystery of the gospel made known unto them by the miraculous application of it to their hearts and minds by God the Holy Spirit – they have an earnest from God – a guarantee that cannot fail.
To have received the earnest of the Holy Spirit is indeed precious to these objects of God’s mercy and grace. This work of the Spirit is one in which they are altogether passive. And yet by God-given faith they confirm the certainty of their being sealed (of being certain for heaven’s glory), when, from the same almighty power that raised Christ from the dead, they are enabled to trust solely in Christ for the salvation of their souls, in repentance turning from the way that before seemed right to them to God’s Gospel – the gospel of their salvation.
--- Randy Wages
What Christ as our Surety engaged to God to do for us?
Whatsoever Christ as Mediator covenanted with the Father to do, that He considered as the Surety of the said Covenant and engaged to perform,
To vindicate the honor of God in all the Perfections of His nature, particularly to preserve the justice and veracity of God, and the sanction of His holy law.
He engaged as the Surety of the Covenant to restore to man, or to all God’s Elect, that righteousness which man lost, that as we were made sinners by Adam’s disobedience, so by Christ’s obedience we should all be made righteous; that as the sin of the first Adam was imputed to our condemnation, so Christ’s righteousness, as our covenanting Head, might be imputed to all His seed, and all this according to the contrivance of God’s infinite wisdom, and to answer the design, purpose, and proposal of God the Father, in the Council of Peace.
Seeing man was a rebel, and in arms against God, and filled with rage and madness, and having enmity in his mind against God, Being alienated from the life of God, Rom. 8:7; Jesus Christ, as our Surety, engaged to change the hearts of all He undertook for, and bring them to accept of the terms of Peace with God through the blood of His Cross, I say, He engaged to God to bring home all whom the Father gave unto Him. Hence, He says, Them I must bring, and shall hear my voice, John 10:16. He must bring them because of the Covenant He had made with God the Father, and upon the consideration of that obligation, He laid Himself under as their Surety. He must circumcise our hearts to love the Lord our God, for Christ also hath once suffered for sins, the just for the unjust, that He might bring us unto God, I Peter 3:18.
From hence it appears that Christ, by virtue of these articles of Peace, as our Surety, engaged to open Blind eyes, and to bring the Prisoners out of the Prison-House, and to set at liberty those who were first bound; or to set at liberty those who were bound, or by the Blood of His Covenant, to send the Prisoners out of the Pit, where there was no water; for this was agreed should be the effects of His undertakings. See Zech. 9:11, Luke 4: 18: The Spirit of the Lord is upon me, because He hath Anointed me to preach the Gospel to the Poor; He hath sent me to heal the broken-hearted, to Preach deliverance to the Captives, and recovering of sight to the blind, and to set at liberty them who were bruised. He engaged to take away the heart of Stone, and to give us a Heart of flesh to give a New heart, for this the Father promised in the Covenant, and what He promised, Christ engaged to do for us. Without almighty power this cannot be done, He works all our works in us and for us. He engaged to subdue Satan, and divest him, that strong Man Armed of all his power.