Freedom from the domination of the law
I know that nothing good lives in me, that is, in my sinful nature. For I have the desire to do what is good, but I cannot carry it out. 19 For what I do is not the good I want to do; no, the evil I do not want to do—this I keep on doing. 20 Now if I do what I do not want to do, it is no longer I who do it, but it is sin living in me that does it.
Verses 18 to 20 are a close parallel to verses 15 to 17, with one difference. Note that in these verses Paul is not identifying himself with the new self but rather is talking about the old Adam when he refers to his “sinful nature.”
It would not be correct to say, “Nothing good lives in the Christian.” To the extent of having the new self, a Christian is perfectly holy, as acceptable to God as his own Son, whose righteousness he sees when he looks at the believer. It’s the other part of the combination, the sinful nature, which Paul brings into the picture in these verses.