The first thing sin took away from the world was peace: peace with God and peace within. And it is the first thing that Christ restores to man through salvation. When a man finds peace with God, the result is definitely peace within. This peace, a state of untroubled, undisturbed, wellbeing, is certainly one proof of salvation. Isaiah 53:5 reveals that Jesus died for man to be at peace both with God and with himself.