Tertullian

“ From the following words, moreover, you may learn that it is the works of the flesh which are condemned, and not the flesh itself: “Therefore, brethren, we are debtors, not to the flesh, to live after the flesh: for if ye live after the flesh ye shall die; but if ye, through the Spirit, do mortify the deeds of the body, ye shall live.” ”

“ When, however, he thus sets life in opposition to the death which is constituted in the flesh, he unquestionably promises the life of righteousness to the same state for which he determined the death of sin. But unmeaning is this opposition which he makes between the “life” and the “death,” if the life is not there where that very thing is to which he opposes it—even the death which is to be extirpated of course from the body. Now, if life thus extirpates death from the body, it can accomplish this only by penetrating thither where that is which it is excluding. ”

“ Now (that I may answer each point separately) , since salvation is promised to those who are living in the flesh, but walking after the Spirit, it is no longer the flesh which is an adversary to salvation, but the working of the flesh. When, however, this operativeness of the flesh is done away with, which is the cause of death, the flesh is shown to be safe, since it is freed from the cause of death. “For the law,” says he, “of the Spirit of life in Christ Jesus hath made me free from the law of sin and death,” [6] —that, surely, which he previously mentioned as dwelling in our members. ”