Question: "What does Genesis 3:15 mean that "he will crush your head, and you will strike his heel"?"
Answer: In Genesis 3 God metes out various judgments against those who brought sin into His perfect world. Adam, Eve, and the serpent all hear of the consequences of their rebellion. To the serpent God says, in part, “And 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” (Genesis 3:15, KJV).
Even in this judgment, there is mercy. God’s curse on the serpent, in particular, was laced with words of hope. The woman mentioned in Genesis 3:15 is Eve. The serpent, addressed directly, is the animal that Satan used to deceive the woman. Some of the curse was directed at the animal (verse 14); at the same time, the curse of God falls upon Satan, who had taken the serpent’s form or body in Eden (cf. the dragon in Revelation 12:9).
As part of the curse, enmity—mutual hatred and ill will—will exist between the woman and the serpent. Later, the same enmity will continue between the woman’s seed or offspring (mankind in general, since Eve is the “mother of all living,” Genesis 3:20) and the serpent’s seed. Their offspring will remain enemies throughout all generations. The serpent’s (metaphorical) offspring are demonic forces and also those people who follow the devil and accomplish his will. Jesus called the Pharisees a “brood of vipers” in Matthew 12:34 and said they belonged to their “father, the devil” in John 8:44. In short, God says that Satan will always be the enemy of mankind. It follows that people who side with Satan will be at perpetual war with God’s elect and that we are engaged in a very real battle between good and evil (Ephesians 6:12).
Genesis 3:15 is a remarkable verse, often called the protoevangelium (literally, “first gospel”), because it is the Bible’s first prediction of a Savior. The second half of the verse gives two messianic prophecies concerning that Savior:
The first messianic prophecy in Genesis 3:15 is that “he will crush your head.” That is, the seed of the woman will crush the serpent’s head. The Amplified Bible makes it clear that “the woman’s seed” is more than mankind in general; it is an individual representing all mankind:
“And I will put enmity (open hostility)
Between you and the woman,
And between your seed (offspring) and her Seed;
He shall [fatally] bruise your head.”
The second messianic prophecy in Genesis 3:15 is that “you will strike his heel.” That is, the serpent will bite the heel of “the woman’s seed.” The heel-bite is set in contrast to the head-crush, as the Amplified Bible brings out: “And you shall [only] bruise His heel.”
This passage points to the promise of Jesus’ birth, His redemption, and His victory over Satan. The woman’s offspring is Jesus. Being virgin-born, He is literally the offspring of a woman (Matthew 1:25; Galatians 4:4; cf. Isaiah 7:14). Being the Son of Man, He is the perfect representative of humankind. The devil’s offspring were the evil men and demonic forces who, like a snake, lay in wait for the Savior and struck at Him. Their venomous conspiracy condemned Jesus to be crucified.
But the serpent’s strike did not spell the end of the Offspring of the woman. Jesus rose the third day, breaking the power of death and winning the ultimate victory. With the cross, Jesus “crushed” the devil’s head, defeating him forever. So, in Genesis 3:15, the crushing of the serpent’s head was a picture of Jesus’ triumph over sin and Satan at the cross (cf. John 12:31). The striking of the Messiah’s heel was a picture of the wounding and death of Jesus on the cross. Satan bruised Jesus’ “heel,” but Jesus showed complete dominance over Satan by bruising his “head.”
Satan, although still active in this world, is a defeated foe. His doom is sure: “And the devil . . . was thrown into the lake of burning sulfur” (Revelation 20:10). Until that time, there remains enmity between Satan and God’s children.
The protoevangelium shows us that God always had the plan of salvation in mind and informed us of His plan as soon as sin entered the world. Satan formulated a plan involving the serpent in Eden, but God was way ahead of him, having already ordained the Serpent-crusher. Jesus Christ perfectly fulfilled God’s mission: “The reason the Son of God appeared was to destroy the devil’s work” (1 John 3:8).