The Sabbath was given to man so that he could rest and renew his relationship with his creator. Many religions today teach that man has an immortal soul that will keep on living after we die. It is interesting to study carefully what the Bible teaches us about this point. Yet God informed the man He created that if he was disobedient he would die. There is a big difference between living for ever under certain conditions and having immortality.
Immortality means that it is totally impossible for that being to die under any circumstances.
Man was made a mortal being. Unless we have food, air, water, and a proper environment, we cease to live. From that moment on their life began to end. Part of Satan's lie was to tell Eve that she would become immortal. This lie has been perpetuated ever since.