In Romans 8:10, what is the body that is dead because of sin?

In Romans 8:10, the body that is dead because of sin is the old Adam. The verse says that if Christ is in you, the body is dead because of sin, but the Spirit is life because of righteousness. This contrasts the old Adam with the Spirit's life.

Les explains that Romans 8:10 follows the teaching about identification with Christ. Just as a seed must be buried in the soil to bring forth new life, Christ died, was buried, and rose again; believers are identified with Him in that death, burial, and resurrection. In that light, the body dead because of sin is the old Adam, while the Spirit is life because of righteousness.

Romans 8:10

And if Christ be in you, the body is dead because of sin; but the Spirit is life because of righteousness.

Why is the body dead in Romans 8:10?

The body is dead because of sin, referring to the old Adam and the flesh under the curse. This physical body will die unless the Lord translates us, as death entered through the fall of man, so all men must die.