What does Romans 8:10 mean?

This passage has indicated that the presence of God's Holy Spirit in a person is necessary for that person to be a Christian. Every truly saved, born-again believer—every real "Christian"—has the Spirit. Without the Spirit, that person does not belong to Christ.

Now Paul writes two things that are true of those with Christ living within them. On the one hand, the body is dead because of sin. This likely means that our human, physical, temporary body is dying and will eventually die as the result of sin in us and in the world. Our bodies are not yet renewed—though they will be (1 John 3:2; 1 Thessalonians 4:16).

On the other hand, the Spirit is life—or gives life—because of righteousness. This phrase is a little trickier to translate. Some Bible teachers understand the Greek word for Spirit here, pneuma, as a reference to our human spirits. In that case, this verse would read that our spirits are alive. Others translate pneuma here as God's Spirit once more, meaning that that the Spirit gives us life. In the original Greek, there was no punctuation, and no lowercase letters—meaning there is no quick-and-easy way to know the writer's intent. Context is key.

In either case, the idea is that having Christ in us means that we are spiritually alive, in the Spirit, even though our sin-ridden bodies are still dying because of sin. Without Christ, without the Holy Spirit, we are spiritually dead. There is no spiritual life in us. The fact that there is spiritual life in us is because of righteousness. That does not mean it is because we are righteous. It means that we have been given credit for Christ's righteousness (Romans 5:21).