“For those who live according to the flesh set their minds on the things of the flesh, but those who live according to the Spirit, the things of the Spirit” (Rom. 8: 5)

Note that this depends on the previous statement, “that the righteous requirement of the law might be fulfilled in us who do not walk according to the flesh but according to the Spirit” (Rom. 8:4). The things of the Spirit are the commandments of God, because the law is spiritual. The flesh serves the law of sin (see Gal. 5:19-21, where the works of the flesh are described). But Christ came in the same flesh, to show the power of the Spirit over the flesh. “Those who are in the flesh cannot please God. But you are not in the flesh but in the Spirit, if indeed the Spirit of God dwells in you” (Rom. 8:8,9).

Now no one will claim that the flesh of a person is any different after his conversion from what it was before. Least of all will the converted person himself say so; for he has continual evidence of its perversity. But if he is really converted, and the Spirit of Christ dwells in him, he is not more in the power of the flesh. Even so Christ came in the same sinful flesh, yet He was without sin, because he was always led by the Spirit.

“The carnal mind is enmity against God; for it is not subject to the law of God, nor indeed can be” (Rom. 8:7). The flesh never becomes converted. It is enmity against God; and that enmity consists of opposition to His law. But Christ is our Peace. In His own flesh He abolishes the enmity, so that all who are crucified with Him are at peace with God; that is, they are subject to His law, which is in their hearts.

Waggoner, Waggoner on Romans, p.129