The “first gospel” came immediately after the first sins, in the context of a curse on the serpent. “I will put enmity between you and the woman, and between your offspring [LXX seed] and her offspring; he shall bruise your head, and you shall bruise his heel” (Genesis 3:15). Jesus Christ is the promised one who came “to destroy the works of the devil” (1 John 3:8), “God’s seed” who abides in the one who has been “born of God” (1 John 3:9). On the other hand, Cain (Genesis 4) was “of the evil one and murdered his brother” (1 John 3:12). Cain was the serpent’s seed.
Cain could easily have been mistaken for God’s promised seed. He was, technically, the first offspring of the woman. But by his actions he proved himself instead to be the serpent’s seed. It became evident immediately that ordinary physical generation alone was not what qualified one to be God’s promised seed. “Not all her offspring are her offspring” (cf. Romans 9:6).
This is the beginning of the gospel of promise; the gospel that works against our entitlements and expectations; the gospel of a God who has always worked through faith, not just flesh.
