There is a belief that the old sinful nature is eradicated the moment a person becomes a Born-Again Christian and that they now have only one wholly sanctified nature. It is believed that one way to view "nature" is to understand it as a "capacity" within the Born-Again Christian, which means that the 'old man' is interpreted as the former way of life because they have two competing capacities within them - the old capacity to sin and the new capacity for godliness so they can resist sinning and put it to death, once and for all, but God did not create a dualistic, bipolar and schizophrenic Christian with two natures; He recreated just one totally new person in righteousness and holiness.
Indeed, the Bible does not use the explicit words "sin nature" (See Rom 7:14-25, 8:3; 2 Pet 2:18). However, the Bible also does not use the word "trinity" or "rapture" either, but the concepts are still implicitly presented throughout Scripture.
The Bible teaches that every human being has an earthly nature that wants to sin as a result of the Fall when Adam and Eve willingly chose not to trust God and believe His Word (Col 3:5). The earthly nature is commonly referred to as the 'flesh' (Heb' basar') in the Old Testament and is used to denote the actual physical body of all living things, and particularly humanity as a whole (Gen 2:21, 6:12-13; 41:2; Ps 16:9, 102:5).
The Hebrew word 'basar' is also used is used interchangeably with "soul" and "body," and about human relationships, emotions and responses (Lev 13:8; Judges 9:2; Isa 40:6; Ps 63:1; 84:2), as well as in reference to mutability and weakness, and also infers the idea of softness (2 Chron 32:8; Isa 31:3; Ezek 11:19; Ps 78:39).
In the Hebrew thought, the understanding of a human being is that there is nothing merely physical because humans do not have flesh, but are flesh. God created human beings (i.e., flesh) as good, just as all other parts of His creation (Job 10:8-12; Ps 119:73; Isa 45:12). God desired that human flesh be fully dependent upon Him for everything (Gen 2:7; 6:3; Isa 31:3). However, because of the Fall, the flesh was exposed to the endless assault of sin and is now frail and transitory (Gen 6:3,5,13; Ps 78:39; Isa 40:6). All of the New Testament uses of the word 'flesh' are built upon the foundation of Old Testament understanding.
The Death of the Flesh
Every human being in this mortal life begins to die from the ravaging effects of sin's sickness and disease on human flesh from the moment they are born. No one is immune from death (unless they are 'raptured' out of this world)! However, at the very moment, a person becomes spiritually Born-Again; they are given eternal life because they were forgiven of all their sins!
Within the science of Physics, there is a branch known as the Laws of Thermodynamics. The second law is known as entropy, which is an empirical biological reality and scientific absolute. Entropy is why things deteriorate, and the body breaks down as it ages. People go bald, hair turns gray, glasses are needed to see, skin wrinkles, bones get brittle, teeth decay, and organs ultimately fail. Everything dies because cells stop dividing, and organs stop working impairing normal functioning, which is the definition of disease. No matter how much 'faith' a person conjures up, they can't escape it. Natural death of the flesh can't be cured.
A person puts on spiritual immortality when they become Born-Again. Death is the ultimate sickness. However, the mortality of this life that ends in death is swallowed up by eternal life when a person dies in Christ (1 Cor 15:53-55).
The sin nature of humankind is not born-again when a person receives Jesus as their personal Lord and Savior through repentant humility. Everyone on this planet sins before God. Sin still reigns in the body of the Born-Again Christian, who is a 'saved' sinner, but still a sinner, none-the-less. That can be seen in the Apostle Paul's statement about the battle of the flesh:
"So I find it to be a law that when I want to do right, evil lies close at hand. For I delight in the law of God, in my inner being, but I see in my members another law waging war against the law of my mind and making me captive to the law of sin that dwells in my members. Wretched man that I am! Who will deliver me from this body of death? Thanks be to God through Jesus Christ our Lord! So then, I myself serve the law of God with my mind, but with my flesh I serve the law of sin." (Rom 7:21-25 ESV)
The biblical truth is that every human being has a mortal and perishable body that is subject to weaknesses and is being torn down and destroyed by sin (1 Cor 15:42-43; 2 Cor 4:16-5:1) which is the reason why the Apostle Paul told that Galatians that "it was because of a bodily ailment that I preached the gospel to you at first, and though my condition was a trial to you, you did not scorn or despise me, but received me as an angel of God, as Christ Jesus" (Gal 4:13–15).
If a human being does not die from an accident, they will still die of so-called "natural causes" which is a euphemism for dying of sickness and disease, when the body finally decays and atrophies to the point of ceasing to function correctly, and one sickness or another kills them. No amount of faith or obedience will undo that process.
The Bible says that the full realization of what Jesus accomplished in the atonement for the Born-Again Christian will happen at their resurrection when a glorified imperishable body replaces the perishable body (1 Cor 15:42-43; 2 Cor 4:16-5:1).
"And He will wipe away every tear from their eyes, and there will no longer be any death; there will no longer be any mourning, or crying, or pain; the first things have passed away." (Rev. 21:4)
New Testament Usage
In the New Testament, the Greek word translated as 'flesh' is 'sarx' and occurs 147 times. It is used in several ways, so it is vitally important that the student of the Bible pay careful attention to the context of a verse to understand the precise nuance of how the word is used.
The word 'sarx' is defined as "the substance of the body," whether of beasts or men (1 Cor 15:39; 2 Cor 10:3; Gal 2:20; Phil 1:22). The word is also used as a figure of speech (synecdoche) denoting the totality of all that is essential to humankind, including the holy humanity of Jesus Christ; as well as the complete person who is made up of spirit, soul, and body (Matt 24:22; John 1:13-14, 6:51-57; 2 Cor 7:5; Heb 5;7; Rom 3:20, 6:19; 1 Tim 3;16; James 5:3; 1 Jn 4:2; 2 Jn 7).
The word 'flesh' can also denote the physical flesh (1 Cor 15:39; 2 Cor 12:7; Gal 4;13-14), humanity as a whole (Rom 3:20; Gal 2:16), human descent (Rom 1:3; 9:3), and social relationships (Rom 4:1; 9:3-5).
Human life in the flesh is normal human existence as God created it, and is not evil (Gal 2:20). However, the term 'flesh' also has the sense of it being frail and provisional (1 Cor 1:26; Gal 1:16; Phil 3:3). The flesh is considered the seat of sin (Matt 26:41; Rom 6:19; 7:5, 8:3,8-9; 2 Peter 2:18; 1 John 2:16). It is also the gateway to sin and is its instrument to wreak havoc by becoming sinful itself, as an occupying army in war (Rom 6:12-14, 7:17-20, 8:3,5-17; 2 Cor 12:7; Gal 4:14, 5:16-24).
The word 'flesh' is also used to denote the externals of life and natural attainment of human beings, as well as the lower and temporary element in the Born-Again Christian (1 Cor 1:26; 2 Cor 7:1; 10:2,3; Gal 3:3; 6:8; Eph 6:5; Heb 9:13).
Sometimes the word 'flesh' is used as a figure of speech (metonymy) referring to the outward natural sinful element of human nature as contrasted with the heart and spirit, the inward and real person, as well as with the mind (Matt 19:5, 16:17; Jn 6:63; Rom 2;28-29, 6:19, 7:25; 1 Cor 10:18; 2 Cor 5:16, 7:1; Gal 4:23; Col 2:1,5; Eph 2:3). When the Bible uses the phrases' being in the flesh' and 'living according to the flesh,' it means being unrenewed, living, and acting as one who is full of sin (Rom 7:5; 8:4-5,7-12).
The mind of the 'flesh' of the Born-Again Christian should be dominated by the Holy Spirit (Col 2:18). The Kingdom of God cannot be inherited by flesh and blood (1 Cor 15:50). The physical flesh of the human body is not inherently sinful but has been corrupted by sin that entered the DNA of humanity as a result of the Fall. The Bible uses the words "flesh" and also "carnal flesh/mind" (Gk: sarkinios) to emphasize its weakness and inferiority, which is opposed to the superiority of the Holy Spirit (Isa 31:3; Matt 26:41; Mark 14:38; Rom 6:19, 7:14).
Human nature is inferior and must be held back in subjection to the new spiritual nature by the power Jesus secured for overcoming it (Rom 8:3; Gal 5:17-18). The Born-Again Christian is to crucify the flesh daily (Gal 2:20; 5:24), so they are now subject to the power of sin in the flesh (Rom 6:14; 8:9). They are implored to "throw off" the "old sinful nature (Gk: 'anthropos' means human being) and their "former way of life, which is corrupted (Gk: 'phtheiro' means to ruin, especially figuratively, by moral influences, to deprave) by lust and deception. Instead, they are to "let the Spirit renew' their "thoughts and attitudes" and then "put on" their "new nature, created to be like God - truly righteous and holy" (Eph 4:22-24 NLT).
The behavior of the Born-Again Christian does not dictate their identity. It was by the sacrifice of Jesus on the cross that they were made positionally perfect and stand before God sanctified, justified, holy, and righteous forever (Heb 10:14). At the very same time, they have a 'flesh/nature' that is sinful, which is why the Bible commands them to 'purify" themselves "from everything that contaminates body and spirit, perfecting holiness out of reverence for God' (2 Cor 7:1 ).
The old sinful flesh/man/nature and its effects on the Born-Again Christian will one day be finally eradicated when they are free from their human body. Someone once said Salvation is in three tenses in the Bible; the Born-Again Christian was saved (from the penalty of sin); they are being saved (from the power of sin); and they will be saved (from the very presence of sin – when they get their new bodies).
The Bible tells the Born-Again Christian that their "old man/flesh" "was crucified with Him' (Rom 6:6). Those who belong to Jesus "have crucified the flesh with the affections and lusts' (Gal 5:24). However, they are also told to 'put off… the old man, which is corrupt according to the deceitful lusts' because there is a daily battle going on within them where 'the flesh lusteth against the Spirit and the Spirit against the flesh: and these are contrary the one to the other: so that ye cannot do the things that ye would' (Gal 5:16, Eph 4:22; also Eph 7:16 KJV). The fact that God has placed them 'in Christ' and has crucified their old nature/man/flesh in Him doesn't mean that it doesn't exist anymore within them, it just becomes ineffective/annulled, yet it continues to endure until death do us part (Rom. 6.6).
The human body is not yet redeemed, but it waits for redemption at the return of the Lord Jesus (Rom 8:23; 1 Cor. 15.22, 23, 42-44, 51-56; 1 Thess. 4.14-18; Phil. 3.20-21). The Born Again Christian is warned not to believe that they have no sin nature, "If we say that we have no sin, we deceive ourselves, and the truth is not in us" (1 Jn 1:8-10 ESV). The belief that there is only one nature or the old nature has been eradicated will cause a person to blame sin in their life on demon spirits, or the past influence of parents, rather than acknowledging it originates in the old nature/flesh and taking full responsibility for it through repentance and forgiveness.
"But the things which proceed out of the mouth come forth out of the heart; and they defile the man. For out of the heart come forth evil thoughts…" (Matt 15:18-19 ESV)
"So now it is no more I that do it, but sin which dwelleth in me. For I know that in me, that is, in my flesh, dwelleth no good thing…" (Rom 7:17-18 ESV)
"Let no man say when he is tempted, I am tempted of God; for God cannot be tempted with evil, and he himself tempteth no man: but each man is tempted, when he is drawn away by his own lust, and enticed. Then the lust, when it hath conceived, beareth sin…" (James 1:13-15 KJV)
The Bible teaches that the Born-Again Christian is a changed person with two natures: one, received by natural birth, which is "deceitful and desperately wicked" (Jer 17:9); and a new nature when they are possessed by Jesus, who recreated them in righteousness and holiness that is received through the new birth.
