Why will the body die if the Lord does not come to translate us?
The body dies because it is the old Adam, the flesh under the curse of sin. Death entered through the fall of man, so all men must die. Unless the Lord comes to translate believers, this physical body will die, since Christ in you is the hope of glory.
Les explains, going back to Romans 8:10 after Colossians 1:27, that if Christ be in you, the body is dead because of sin. That body is the old Adam again; Adam and the flesh were all under the curse. This body is going to die if the Lord doesn't come to translate us. It is all part of the fall of man: death came in, and so all men have to die. The mystery revealed to Paul is Christ in you, the hope of glory, a truth not found in the Gospels, the Old Testament, or the rest of the Bible except the epistles of Paul.
And if Christ be in you, the body is dead because of sin; but the Spirit is life because of righteousness.
More Questions
What does it mean that the body is dead because of sin in Romans 8:10?
In Romans 8:10, the body that is 'dead because of sin' refers to the old Adam, and Adam and the flesh were all under the curse, so this body will die unless the Lord comes to translate us.