In our day, few seem concerned with the question, "How can a sinner like me live with God forever?" But that question is central to the biblical storyline. The doctrine of atonement answers that question, and what many fail to see, is that this idea started all the way back in Eden where out of judgment a triumphant promise sounds forth: the seed of the woman—the Messiah – will crush the serpent's head!
While many critique the Christ-centered interpretation of the Old Testament as reading back into the text what's not there, these critiques fail primarily because they assume the OT on its own terms is not Christ-centered. But that's exactly what it is! So when we think about Christ's atonement we must go back to the beginning. In Eden, God establishes an expectation for a coming Messiah and atonement.
The atonement foreshadowed in Eden advances four themes throughout Scripture.
First, Christ will defeat our enemy by crushing the serpent's head (Gen 3:15).
Throughout the Bible, whether it's the promise of a king who will crush the "forehead" of Israel's enemy (Num 24:17), or Jael driving a tent peg through Sisera's temple, or David's stone sinking into the head of a man described as a giant sea serpent (1 Sam 17), or the promise that Messiah's enemies will be under his feet (Psa 110:1), God is constantly bashing skulls (cf. Psa 68:21; 74:13-14; 91:13; Hab 3:13). The OT presents the salvation of God's people by the means of Messiah crushing their enemies' heads.
Second, the shedding of blood is necessary to cover human shame.
Once mankind sinned, the sound of God walking in the garden brought fear and shame. Adam and Eve hid from the Lord behind fig leaves and trees (Gen 3:7-8), but God graciously clothes his ashamed creatures with animal skins (Gen 3:21). Though there is nothing explicitly stated in the text, this is an early indicator of what will take place in the sacrificial system. Animals will be sacrificed and their blood shed in the place of sinful man, culminating with the blood of the Messiah – the Lamb of God.
Third, Genesis 3 anticipates banished humanity regaining access to a holy God.
God's intention from the beginning was to live with his people (cf. Rev 21:3), but human sin required sword-wielding Cherubs to keep humanity out from God's presence (Gen 3:24). But, God begins a covenant relationship (marriage) with Israel at Sinai, and then makes plans to build a tent and move in with them. The Tabernacle is described like Eden, and again the Cherubs – woven into the veil – keep sinful humanity out (Gen 3:24; Exo 26:31-33). The answer to the question "how can a holy God live with sinful people" is the system of atonement described in Leviticus. Humanity is allowed into God's presence once a year by means of blood sacrifice. Yet, when Christ – the Lamb of God – breathes his last on the cross, the veil is torn in two so that now sinful man has been readmitted to the presence of God. We now have confidence to enter God's presence by the blood of Jesus through the curtain of his flesh (Heb 10:19-20).
Finally, Genesis 3 presents the idea of suffering.
Yes, the promised "Seed" will crush the Serpent's head, but only through suffering—his heel will be bruised (Gen 3:15). While substitution is not taught explicitly in Genesis 3, it is implied because God promises the Savior's bruising before He ever mentions judgment against humanity. This expectation plays out in the OT narrative. For example, the ultimate threat to the people of Israel for their sin was – as in the Garden – exile (cf. Deut 28; Ezek 37). Yet, in 1 Samuel 4 sinful Israel does not go into exile; instead, the Lord himself in his visible presence on earth – the ark of the covenant – goes into exile for his people (1 Sam 4:22). And on the 3rd day in exile he crushes the head of Dagon and begins to unleash plagues on the Philistines (1 Sam 5). God defeats his people's enemies by taking the covenant curses on himself (i.e. Penal Substitution). And this is how the ultimate victory is secured when the serpent is overcome by the "blood of the lamb" (Rev 12).
The Messiah's work on the cross to bring humanity back to God is the culmination of the expectation that began in Eden's Garden. Being so, at Christ's sacrifice we are not shocked to find a garden for testing, thorns (Gen 3:18), a tree, the promised seed, Cherubs on the veil, and yes, even death. But on Sunday morning, when the Promised Seed walks out of the tomb into a garden, the cherubs have left their post and the ancient dragon's temple has been crushed by a pierced heel!