Why does every human being have to die?
Every human being must die because the law declares that the soul that sins shall surely die, and all people are sinners as sons of Adam. Adam's transgression brought death upon the human race, so death is universal. God provided a substitutionary death in Christ, yet believers still must experience that death.
Les explains that this goes back to the first law God gave the human race, when He told Adam and Eve, 'The day that thou eatest thereof, thou shalt surely die.' Then the principle is restated, which Les says he thinks is in Ezekiel: 'The soul that sinneth shall surely die.' Since the law determines that every human being is a sinner because we are sons of Adam, it means every human being has to die. Les calls this a loophole: God provided that Christ died in our place, which is substitution. Yet believers still have to experience that same death He experienced in the person of Christ.