From session 2 of Michael Horton’s Christless Christianity DVD series:

It’s the gospel that’s surprising; it’s the gospel that comes to us and throws us off our horse, because the gospel isn’t wired into us. The gospel only came about because after the Fall—though God could have invoked the judgments that he threatened in the Law—he instead promised a Savior and clothed Adam and Eve, took all their fig leaves, and clothed them with the sacrificial skins of animals pointing forward to Christ. That was a surprise, a complete surprise. God could have wiped them off the face of the earth at that point and that’s why they ran because their law compass said, “we’d better run.” That’s why religions, you know, throw kids into volcanoes; and have things like penance where they’ll go through and make all kinds of satisfaction—crawl on their knees, bloody their knees–do whatever needs to be done; go on suicide missions; do whatever it takes in order to appease this God they know they’ve offended.