What makes sin sin, in the deepest sense, is that it is against God. We let ourselves off the hook too easily when we think of sins along horizontal axes only—whether the horizontal sins of socially disapproved behavior or the horizontal sin of genocide. What makes sins really vile, intrinsically heinous—what makes them worthy of punishment by God himself—is that they are first, foremost, and most deeply sins against the living God, who has made us for himself and to whom we must one day give an account. In other words, this psalm [51] of repentance from sin discloses important things about sin’s relation to God.

—D. A. Carson