The Old Testament uses the word “flesh” to mean only one thing—the physical body, because it was not until Christ that the “flesh”—sinful nature—was addressed with the application of being finally “condemned” (Rom 8:3).
For example, the phrase in the above reference, “sinful flesh,” does not mean the physical body, this would conflict with “you are not in the flesh” (Rom 8:9), meaning you are no longer living for or after the dominion of the sinful nature, but rather for or after “the Holy Spirit.”
The concept that the physical body is sinful or evil is a misunderstanding, and reasonably so when considering the often obscurity of Scripture. It is the nature which determines good or evil of a spirit (person), the body just manifests what the spirit is, thus the body is subject to the person, whether it will be used for good or evil.
“In the likeness of sinful flesh” (Rom 8:3); “Which expresses the reality of His incarnation, of His having a true real human nature; for flesh is not to be taken strictly for a part of the body, nor for the whole body only, but for the whole human nature, soul and body; which though it looked like a sinful nature, yet was not sinful.
“The likeness of it denotes the outward appearance of Christ in it; who was born of a sinful woman (Rom 3:23); was subject to the infirmities of human nature, which though not sinful, are the effects of sin; was reckoned among transgressors, was traduced as one Himself by men, and treated as such by the justice of God; He having all the sins of His people on him, for which He was answerable.” JG
“Let not sin therefore reign in your mortal body, that ye should obey it in the lusts thereof” (Rom 6:12). “The ye should obey it” (I believe “it” is in reference, not to the body but to sin). I believe “the lusts thereof” is “the body of sin” (Rom 6:6), which pertains to the sinful nature, thus these are “your members which are upon the earth; fornication, uncleanness, inordinate affection, evil concupiscence, and covetousness, which is idolatry” (Col 3:5).
Reference: “Flesh,” Strong’s G4561, sarx, IV. The flesh, denotes mere human nature, the earthly nature of man apart from divine influence, and therefore prone to sin and opposed to God.