He that committeth sin is of the devil; for the devil sinneth from the beginning. For this purpose the Son of God was manifested, that he might destroy the works of the devil, I John 3:8. In this verse we find the second part of God's threefold purpose. Once again, God's purpose harkens back to his war with the devil. There are many places in the Word of God where it speaks of why Jesus Christ came. Each of them is a facet of how he destroys the work of the devil.
For the Son of man is come to seek and to save that which was lost, Luke 19:10. What better way to destroy the works of the devil than to seek out the devil's children and convert them? To this end was I born, and for this cause came I into the world, that I should bear witness unto the truth, John 18:37. The devil is the father of lies (John 8:44). To bear witness to the truth destroys the devils works.
In the Garden of Eden, the devil took Adam, the son of God by creation (Luke 3:38), and made him into a son of Belial. He used a gospel of doubt based on a tree. Turn about is fair play. God uses a gospel of faith based on a tree to take the devil's children and make them his own. The very purpose that Jesus Christ was manifest in the flesh was to destroy the works of the devil. Our salvation is a wondrous byproduct of the coming of Jesus Christ, but his purpose was to destroy the works of the devil.
Come, Desire of nations, come! Fix in us Thy humble home: Rise, the woman’s conqu’ring seed, Bruise in us the serpent’s head; Adam’s likeness now efface, Stamp Thine image in its place: Final Adam from above, Reinstate us in Thy love.
From Hark the Herald Angels Sing