God showed mercy to Adam and Eve even in giving the curse in Genesis 3 in a number of significant ways. First and most basically, God didn't destroy the creation he had made. He certainly, in his holiness, would have had the right to do so, but he did not. Secondly, not only did he not destroy the creation, but he goes and finds Adam and Eve, and he speaks to them. Already we have redemptive revelation being initiated by God. The hound of heaven will not let these rebellious humans go. Even when they would prefer to hide in their guilt and shame, God pursues them. Thirdly, we can say God doesn't just speak to them, but God provides even further for reconciliation. God provides the garments to cover them in their shame, and this may also indicate the beginnings of atonement, something gesturing toward sacrifice, so that not only shame, but guilt is going to be addressed. Fourthly, we can say that God will not leave rebellious humans in their self-destruction. His barring them from the Tree of Life is not merely judgment. It is also, ironically perhaps, life-giving. We see that this is so if we look at the Tower of Babel episode, and we see what aggregated human potential might choose to pursue and might threaten to accomplish if left to itself. So, God barring humans from the Tree of Life now, keeps them from destroying themselves in combining moral autonomy with this drive for immortality. Instead, the flaming cherubim suggests that people will now only be able to come into God's presence when they pursue the cultically-provided means through having their sins atoned for that God makes possible. Then and only then, may people come into God's presence and have life. So, fifthly, we might speak of God showing this mercy in terms of the concept of preservation. God doesn't destroy the creation, but God doesn't simply leave it in its fallen state, and God doesn't instantly and comprehensively redeem it, but God preserves it for the sake of redeeming it. And that signals something very significant about what God is ultimately going to accomplish in his redemption. He's not going to redeem us out of earth and its cursed history, he's going to redeem us by transforming that earth and the meaning of its history into a new heavens and a new earth wherein righteousness dwells.