The First Gospel
Genesis 3:15, the seed who crushes the serpent, as the early church read it
In the same breath that God curses the serpent in Eden, He makes the first promise of a Rescuer: a "seed of the woman" who will crush the serpent's head, though His own heel be bruised in the doing. The church has called this verse the protoevangelium, the gospel before the gospel. Irenaeus of Lyons (writing around AD 180, a hearer of Polycarp, who had heard the apostle John) makes it the spine of his whole theology: Christ, the new Adam born of a woman, undoes in Himself what the first Adam lost, and treads down the serpent's head. His words below, with a plain restatement.
The Father's words are verbatim and attributed (Irenaeus, Against Heresies, in the Ante-Nicene Fathers, public domain; selected from the running prose, footnote apparatus omitted). The box marked "In plain terms" is our own restatement, never the Father's words.
Genesis 3:15 · KJVAnd I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel.
"He has therefore, in His work of recapitulation, summed up all things, both waging war against our enemy, and crushing him who had at the beginning led us away captives in Adam, and trampled upon his head, as thou canst perceive in Genesis that God said to the serpent… For from that time, He who should be born of a woman, namely from the Virgin, after the likeness of Adam, was preached as keeping watch for the head of the serpent."
St. Irenaeus of LyonsIrenaeus reads Genesis 3:15 as the opening line of the gospel. The "seed of the woman" is not humanity in general but One in particular, the One "born of a woman… from the Virgin," Christ, who "from that time" was promised as the head-crusher. His great word for it is recapitulation: Christ re-runs and reverses the whole story of Adam, retracing our defeat and turning it into victory, so that the very ground where we fell becomes the ground where the enemy is undone.
"For indeed the enemy would not have been fairly vanquished, unless it had been a man born of a woman who conquered him. For it was by means of a woman that he got the advantage over man at first… that, as our species went down to death through a vanquished man, so we may ascend to life again through a victorious one; and as through a man death received the palm of victory against us, so again by a man we may receive the palm against death."
St. Irenaeus of Lyons"The other biting, killing, and impeding the steps of man, until the seed did come appointed to tread down his head, which was born of Mary… and that He should bind 'the dragon, that old serpent,' and subject him to the power of man… When therefore the Lord vivifies man, that is, Adam, death is at the same time destroyed."
St. Irenaeus of LyonsNotice the symmetry Irenaeus hears in the verse: a head crushed and a heel bruised. The serpent could only "bite the heel," wound the Savior in His suffering and death; but the Savior crushes the head, the enemy's very power and life. The cross looks like the serpent's victory and is in fact his ruin. And because the conqueror had to be a true man born of a woman (the fall came "by means of a woman," so the rescue comes by the woman's seed), the door opens here in Genesis to the whole gospel: the Virgin's Son binds "that old serpent" and, by raising Adam, destroys death itself.
Where the traditions diverge
That Genesis 3:15 is the first promise of Christ, the seed of the woman who would crush the serpent, is common ground for Catholic, Orthodox, and Protestant alike, and the New Testament itself draws the line: Paul tells the Romans that "the God of peace shall bruise Satan under your feet shortly" (Romans 16:20), and John sees "that old serpent" finally cast down (Revelation 12:9, 20:2). Two divergences are worth naming honestly. First, a textual one: the Hebrew and the Greek read "he [or it, the seed] shall bruise thy head," pointing to Christ, and that is how Irenaeus reads it; the old Latin Vulgate rendered it "she shall crush" (ipsa conteret), which fed a tradition of reading Mary as the crusher. The earliest reading, and the one the Hebrew supports, puts the victory in the seed, Christ, while Irenaeus separately and rightly honors Mary as the new Eve through whom that seed came. Second, a modern one: the naturalistic reading empties the verse of any promise at all, reducing it to a folk explanation of why people and snakes are at odds. The drift to resist is that flattening, when the apostles and the earliest Fathers heard in Eden's curse the first announcement of the cross. (See Adam and Christ and the triumph of the cross.)
Patristic text from Irenaeus, Against Heresies (Books IV-V), in the Ante-Nicene Fathers (public domain), selected from the running prose with footnote apparatus omitted; nothing added or paraphrased within the quotation marks. Scripture in the King James Version; the plain-language lines are our own restatement. This passage in the Study Bible; Genesis 3 at BibleHub.