GEN1090 The only factor that can ultimately prevent someone from murdering is fear of God.   After God warned Avimelech to restore Sara to her husband, Avimelech summoned Avraham, and demanded an explanation for his claiming to be Sara’s brother.   Avraham told Avimelech that individuals or nations might appear to be great philosophers and humanitarians; they might even have proper manners and good character traits.  But as long as their morality is based on their own logic, we can never be certain that when their desire to do evil is strong, their logic will be able to overcome that desire.  There is only one restraint that we can rely upon to prevent a person from committing a crime: fear of God.  When a person has an overpowering desire to do something wrong, but realizes that God is aware of every hidden act, he will be ashamed to commit the offense.   Avraham therefore said in effect: “Even if you are righteous, since you lack fear of God, I fear that you will murder me to take my wife.” Malbim, commentary on this verse.   PLYN 81