Genesis 3:15 is called the protoevangelium — the first gospel. Immediately after the fall, before any law is given, before any covenant is made, God announces the verdict on the serpent: the seed of the woman will crush your head. This is not a vague metaphor. It is a specific prophecy: a descendant of Eve will deliver a fatal blow to the serpent, though he himself will be struck in the process. The "bruising of the heel" points to Christ's suffering on the cross. The "crushing of the head" points to his total victory over sin and death through the resurrection. The entire redemptive arc of scripture — from this verse to Revelation 20 — is the outworking of this single promise.