THE EXISTENCE OF THE FLESH
We need to realize that even though we can put to death the flesh and cause it to be annulled (original Greek meaning for "destroyed" in Rom. 6:6 [KJV]), it nevertheless still exists. A very great mistake that people make is that they think that they have extinguished the existence of sin and have uprooted the flesh from within them. This kind of doctrine leads people astray. The regenerated life does not change the flesh. The crucifixion together with Christ does not cause the flesh to disappear. The Holy Spirit who indwells our spirit does not force people to not walk according to the flesh. Whether it is the flesh or "the fleshly nature" as people have called it, it always exists within the believer. Whenever the believer fulfills the condition for it to work, it operates right away.
We have seen how much man’s body is associated with the flesh. Therefore, before we are separated from this body, we can never be separated from our flesh such that it has no possibility to operate again. That which is born of the flesh is flesh. Before the transfiguration of our body, which we received by birth from Adam’s corruption, we shall by no means have the flesh eradicated from within us. Our body has not been redeemed yet (Rom. 8:23). We have to wait until the Lord’s second coming to have this redemption (1 Cor. 15:22-23, 42-44, 51-56; 1 Thes. 4:14-18; Phil. 3:20-21). Therefore, as long as we are in this body for one day, for one day we cannot avoid watching and guarding against all the activities of the flesh in the body.
We should know that our walking may, at most, be like Paul’s. He said, "For though we walk in flesh, we do not war according to flesh" (2 Cor. 10:3). Because he still had the body, he still walked in the flesh. But, due to the corruption and wretchedness of the flesh and its nature, he did not "war according to flesh." Although he walked in the flesh, he did not "walk according to the flesh" (Rom. 8:4). Before the believer is separated from his body, he can by no means be separated from the flesh. Physically speaking, he lives in the flesh (Gal. 2:20). Spiritually speaking, he does "not war according to flesh." If Paul still had the flesh according to which he might war (only he did not do that), who would dare to say that he did not have "flesh"? Therefore, both the cross and the Holy Spirit are needed at all times.
Because of the great importance of this point, we cannot be inattentive. Otherwise, believers will fall into hypocrisy or idleness, thinking that their flesh is gone, that they are therefore perfectly holy, and that there is no need of watchfulness. Herein is a fact: children born of regenerated and sanctified parents are also fleshly and need to be regenerated even as the worldly people. No one can say that the children born of sanctified believers are not fleshly and have no need of regeneration. The Lord Jesus said, "That which is born of the flesh is flesh" (John 3:6). If what is born is flesh, this proves that the one who begets it is also flesh! This is because flesh only gives birth to flesh. Therefore, the children’s being fleshly proves that the parents are not yet free from the flesh. The reason saints pass the fallen nature on to their children is that they had this fallen nature originally. They are not able to pass on to them the divine nature which they received in regeneration, because this divine nature is not their own but is obtained by each one through grace from God. The reason that the believers’ children have a sinful nature is that the believers have a sinful nature and have passed it on to them. This obvious fact proves that the sinful nature in the believers exists.
(Spiritual Man, The (3 volume set), Chapter 7, by Watchman Nee)