The "flesh" stands for a certain orientation of life. It is the sin-bent self characterized by self-sufficiency that wages war against God… The flesh and the spirit denote not two coexisting parts of the individual, but a contrast of tendencies and loyalties which compete for dominance as powers within each person… It creates estrangement from God that is broken only when persons submit in faith to the gospel and allow God's Spirit to seize control.
David Garland