There are two ways of living a human life: one is to live according to the spirit, and the other is to live according to the flesh. We all used to live according to the flesh gratifying its desires, and that time, the only spirit we could follow was the spirit of the ruler of this world (Eph 2:1-3). We were dead spiritually, but became born again in the spirit by God’s word through Jesus Christ. And as born-again Christians, we no longer need to live according to the flesh.

Therefore, brothers, we have an obligation—but it is not to the sinful nature, to live according to it (Rom 8:12, literal translation: we are not debtors to the flesh to live according to it).

The literal translation works fine with this verse. We have no obligation to live according to the flesh. Note, however, that it only says, “we are not debtors to the flesh to live according to it,” and if we still want to live according to it, we can. In other words, living according to the spirit does not come automatically once you become a Christian. When we were spiritually dead, we could only live according to the flesh, but God sent his Son, and made it possible for us to live according to the spirit.

Adam chose to live according to the flesh by eating from the tree of the knowledge of good and evil. The knowledge of “good” comes only from God, and any knowledge against it is evil. In other words, God is the source of “good”, and we humans are simply to let that “good” work though our spirit by spiritually submitting ourselves to him.

We know that the law is spiritual (7:14).

The law is the standard in which God tells us what is good and what is not. As for what is spiritual, we can only receive it spiritually, and do it spiritually. It is unreasonable to keep the law, which is spiritual, by our flesh, which is not spiritual. If we can still keep it, it can be kept only through our spirit. In fact, before the Fall of Man, Adam was able to obey God and do his will without the knowledge of good and evil. He did not need the law. What the law says is basically, “You shall not …” And those you-shall-not’s were not necessary as long as Adam was obedient to God by living according to the spirit. No one who walks according to the flesh is able to keep the law. No matter how hard we try, we always fail because this “trying” is done merely by the flesh in us who walk according to it. So God sent Jesus to us:

… in order that the righteous requirements of the law might be fully met in us, who do not live according to the flesh but according to the spirit (8:4).

Note that this verse does not say, “in order that we believers might keep the law.” Instead, it explains in a passive voice: “the righteous requirements of the law might be fully met in us.” And it does not even say, “… in us who believe,” but “… in us, who do not live according to the flesh but according to the spirit.”

It is unfortunate that many of our translations understand Greek pneuma as “the Spirit.” The primary reason for this is that our translators did not know the existence of our human spirit. Why would anyone contrast the human flesh sarx in Greek (translated as “sinful nature” in NIV) with God’s spirit? At any rate, when you try to reign in life, you fail. Walk according to the spirit, and let God’s spirit work through your spirit. Then, by his grace, you find yourself reigning in life.

… so that, just as sin reigned in death, so also grace might reign through righteousness to bring eternal life through Jesus Christ our Lord (5:21).