8. That it might cause--God purposely let her so shamelessly pour the blood on the bare rock, "that it might" the more loudly and openly cry for vengeance from on high; and that the connection between the guilt and the punishment might be the more palpable. The blood of Abel, though the ground received it, still cries to heaven for vengeance (Ge 4:10, 11); much more blood shamelessly exposed on the bare rock.
      set her blood--She shall be paid back in kind (Mt 7:2). She openly shed blood, and her blood shall openly be shed.

JFB.