What does Romans 8:12 mean?

Prior verses described the differences between two kinds of life. One was living by the sinful, self-serving, world-following flesh, as all non-Christians do. The other was living by the Spirit of God, as all Christians do.

Paul moves next to teaching about how Christians should live since this is true. First, he writes that since saved Christians have been given spiritual life—now in the Spirit and the promise of physical resurrection later by the power of the Spirit— we have an obligation. We have a debt to pay, in a sense.

Before describing what that obligation is, though, Paul wants his readers to hear what they are not obligated to do. Christians no longer owe anything to the flesh. It's important to remember that when Paul writes "flesh," he does not mean simply "body." He does not even mean just sexual sin. He means the self-serving, self-reliant, me-first way of living in the world that all people apart from Christ follow.

We don't owe that old way of living anything. It is not who we are as Christians any longer. In fact, God specifically calls us to abandon that lifestyle and to live in the power of God's Spirit. Christians aren't meant for sin and selfishness any more.