19 For I do not do the good I want,
but the evil I do not want is what I keep on doing.
20 Now if I do what I do not want, it is no longer I who do it,
but sin that dwells within me.
21 So I find it to be a law that when I want to do right, evil lies close at hand.
Paul continues to describe—and emphasize by repetition—the internal struggle between good and evil. The “I” wants to do what is right and good but is obstructed by sin dwelling within. For the most part, these verses restate what Paul has previously said. Verse 19 restates the second part of verse 15, and verse 20 restates verse 17.The meaning of “flesh”
Some commentators take “flesh” in verse 18 to mean the sinful nature, and that is how NIV translated the term until its 2011 revision. For this term’s meaning, context is always the deciding factor. Douglas Moo points to verse 25, which contrasts “flesh” with “mind,” and verse 23, where the “other law,” “the law of sin,” is “in my members.” This contextual evidence suggests Paul has in mind the material body, Moo concludes.
Moo says Paul’s reference to the body is a deliberate effort “to reveal the ‘dividedness’ of Jews under the law as a way of explaining how sincere respect for that law could be combined with failure to perform it.” To highlight this internal divide, Paul resorts to “anthropological dualism,” pitting the mind and will to do good against the body’s corruption by sin to do evil. Because of the body’s susceptibility to temptation, sin is able to overrule and overpower the desire of the mind/will to do what is right.
Moo understands Paul to say that Jews and other non-Christians have a genuine desire to do what is right, even as they remain under the dominion of sin. Paul’s point is not that their mind/will is pure and uncorrupted, but that no matter how hard they strive to do what is right, sin works through the body to frustrate them.
Richard Longenecker, who regards “flesh” as the sinful nature, sees in verse 18 the experience of every spiritually sensitive non-Christian. He notes that the conflict between desire and ability to carry it out found universal recognition among many writers and moralists of Paul’s day. For example, compare verse 19 with how Ovid characterizes Medea’s dilemma: “I see and approve the better course, but I follow the worse.” Or this from Epictetus: “He who sins does not what he would, and does what he would not.”Rabbinic influence
It’s also noteworthy, as Everett Harrison points out, that Paul chose to depict the internal struggle between good and evil in a way similar to rabbinic teaching. Paul’s literary framework parallels rabbinic understanding, even though his remedy is radically different:
Finally, the word law has several shades of meaning and can refer to natural law, the Mosaic law, or principle, such as a general rule of action. Verse 21 likely has an instance of the latter meaning. Whenever “I” wants to do right it encounters the rule that evil lies close at hand. Sin remains ever the tyrant.