Ephesians 1:13-14 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, Which is the earnest of our inheritance until the redemption of the purchased possession, unto the praise of his glory.

After being regenerated; after being adopted as a child of God; after having been given the greatest inheritance of eternal life; if the person will put his trust in this gospel message and then believe, he will receive the earnest (a small amount provided in advance) of the same inheritance that he obtained at adoption, which is reserved in heaven. This earnest of eternal life and eternal salvation is for the present. This is taking possession of life and salvation now. This is the life that the person will have while in obedience to God, and the life he will loose if he is disobedient. This is the salvation he finds, if he is obedient to God, and the salvation he will loose unto destruction, if he is disobedient to God. The earnest which a person receives for obedience is the only part of the inheritance a person can loose, or fall away from, no matter how great the sin, because our inheritance in heaven is given by grace, and not by works of righteousness.

1 Corinthians 3:13-15 Every man’s work shall be made manifest: for the day shall declare it, because it shall be revealed by fire; and the fire shall try every man’s work of what sort it is. If any man’s work abide which he hath built thereupon, he shall receive a reward. If any man’s work shall be burned, he shall suffer loss: but he himself shall be saved; yet so as by fire.

Our salvation is not of works, but of grace. But, there are works which are required of the children of God. All will suffer loss, for all have sinned and come short of the glory of God, and continue to do so every day. They are all sinners, there is none righteous. But, our loss is limited by our obedience, for every work of righteousness will remain. Notice that, “if any man’s work abide“, suggests there will be few who have works that survive the test. And then, even more importantly, notice that even those who suffer total loss will be saved. The disobedient, who do no righteousness, will be finally saved because of the work accomplished by Jesus Christ for them. This is true grace, not of works, lest ye should boast.

Related passages:
John 6:29
Romans 11:6
Romans 4:4

Ephesians 1:5-6 Having predestinated us unto the adoption of children by Jesus Christ to himself, according to the good pleasure of his will, To the praise of the glory of his grace, wherein he hath made us accepted in the beloved.

The chosen of God were predestinated to be adopted as children, when He also predetermined that "in due time Christ [would die] for the ungodly". Therefore, Christ’s predetermined death was the event which resulted in the predetermined adoption, of this predetermined group of ungodly people.

God first chose a people unto Himself. He then predetermined that Christ would die for this elect people. In doing so, He also predetermined that this group of people would be adopted, according to the good pleasure of His will. This means that His benevolence decided His actions. God’s own desire to do good was the driving force behind His decision to provide this gift, which is given freely. This is the core of free grace. It could not be any more plainly stated.

Secondly, Paul says, "wherein", meaning in this same respect, they are also made acceptable in the beloved. It was God who made us accepted, through the sacrifice of Christ for our sins. This does not occur when we believe, but must occur beforehand. Note carefully how Paul builds upon this truth. Next he teaches that as a result of this adoption, we have also "obtained an inheritance". I use Paul’s exact wording, because this conveys ownership without possession. It simply means that the person has been allotted a portion of the Fathers estate. This is the same manner that I have bequeathed my estate to my children through a will. They will not take possession until I have passed away, and they have reached the age of twenty-one. The person, having been adopted as a child, has been added to the legal declaration of how God wishes his estate to be handled. They will take possession when they depart this world, either by physical death or on the last day.

This is the foundation of the gospel, the corner stone upon which we are called to place our trust and belief. And in Ephesians 1:13-14, Paul will reveal how a person can take immediate possession of the "the earnest of our inheritance" – a small amount given in advance.