Before Cain kills his brother, God explains to him that there is a choice to do right, but if that choice is not made then sin is ???at the door.??? The rabbis who authored the Midrash Genesis Rabbah understood this to mean that if we do nothing about even the threat of sin, it will become a habit that we don???t even notice. ???In the beginning, sin is like a drop-in, then it becomes a regular gu