Romans 8:12

Because of what God has done for us (Romans 8:1-11), believers have an obligation to respond appropriately. However we can only do so with the Spirit’s help. Paul stated only the negative side of our responsibility here. He could have gone on to say ". . . but to God, to live according to the Spirit." He planned to stress that in the verses that follow.

This verse teaches clearly that the believer still has a sinful human nature within him even though he has died with Christ. God does not eradicate the believer’s flesh at conversion. Therefore we must not "live [walk] according to" it. Progressive sanctification is not something the Christian may take or leave. God commanded us to pursue it (cf. Titus 2:12; 2 Peter 1:3-11; 2 Peter 3:18).