Salvation is a gift from God that cannot be taken away. When a person is saved, he is always saved. Nothing can separate him from eternal life in Christ and he can live with full assurance of Heaven as his future home.
Before God drove Adam from the Garden, He made a promise. Interestingly, the promise was not spoken directly to Adam. Adam and his posterity would receive the benefits of it, but the promise was spoken to the great evil adversary Satan. God told him that through the woman he had deceived, He would bring a deliverer that would crush his head. Invoking Milton, we can say there was a form of poetic justice in what God said. The one who was weak and had been taken advantage of by a more powerful being— a weak woman would give birth to a Son who would destroy Satan’s tyranny forever. God’s own Son would come to crush the life out of Satan for what he had done.
Genesis 3:15 is the first time the gospel was preached. God preached it in what is known as the protoevangelium. God said to Satan: "And I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel."
The seed of the woman is Jesus Christ. Not since the beginning of time have we heard of the seed of the woman. It is always the seed of the man. But this would not be a son with a human father. This Son would come from above. He would be born from God. He would be a virgin born Son—a virgin impregnated by the Holy Spirit, and He was God incarnate born of a lowly Galilean virgin. (Excerpted from the sermon, Paradise Regained, by Pastor V. Mark Smith)