The seed promise does not move in a straight line. It narrows. Each new revelation specifies the previous one, ruling out vast portions of humanity until the seed is identified down to a particular town and a particular woman.
Read the canon end-to-end and the funnel emerges:
- Gen 3:15 — the seed of the woman (humanity, broad)
- Gen 9:26–27 — the line of Shem (one of Noah''s three sons)
- Gen 12:3 — the line of Abraham (one descendant of Shem)
- Gen 21:12 — through Isaac, not Ishmael (one of Abraham''s sons)
- Gen 28:14 — through Jacob, not Esau (one of Isaac''s sons)
- Gen 49:10 — through Judah (one of Jacob''s twelve)
- 2 Sam 7:12–16 — through David (one of Judah''s descendants)
- Isa 7:14 — through a virgin (further specifying the how)
- Mic 5:2 — born in Bethlehem (specifying the where)
- Luke 1:31–33 — to Mary, in Nazareth, of the house of David (the who)
Each step makes the previous step more specific. None of the steps contradicts a prior step; each excludes a vast set of alternatives. By Luke 1, the OT seed has narrowed to a single named woman in a known town descended from a known king who is descended from a known patriarch who is descended from a named son of Noah who is the seed of the original woman.
The narrowing is the argument. A messianic figure could appear by accident from one or two of these specifications. Ten specifications, all met by one person, in the sequence the OT predicts, is the OT''s case for that person.
→ Go deeper: Davidic narrowing — the load-bearing 7th specification