After humanity's fall, God makes a promise not to Adam and Eve but to the serpent itself: one day, the offspring of the woman will crush it. That promise begins to narrow almost immediately — preserved through Seth rather than Cain, carried through Noah's family alone when judgment falls, and then focused on a single man, Abraham, and the covenant God swears to him alone.
From Abraham the line narrows further still — to Isaac over Ishmael, to Jacob over Esau, to the tribe of Judah, and finally to the house of David, whose throne God promises will never end. As Israel's kings fail one after another, the prophets keep the promise alive, describing a coming King who will be born of a virgin, reign as David's heir, and suffer as a righteous servant for his people.
Every page of that narrowing story converges on one man: Jesus Christ, the singular Seed Paul names in Galatians 3:16. Through his death and resurrection, the promise made in Eden is fulfilled, and — remarkably — the narrowing reverses: in Christ, the single line widens again into a multinational family, Jew and Gentile alike gathered as Abraham's heirs by faith, until the final harvest gathers every true seed into the New Creation.