The Lord Jesus was fully human physically but not spiritually, that is, He had the nature of our body but not the nature of our soul (the soul being the reasoning entity of our spirit). The nature of a human soul is sinful, but the nature of Christ’s soul was sinless! Thus only Christians have two natures in their soul (old and new man)! This “new man” or new nature in those reborn is something “created in righteousness and true holiness,” and “after the image of Him that created him (it)” (Eph 4:24; Col 3:10). Man was created in God’s “likeness,” but the Son of God was incarnated after the “likeness of sinful flesh” (Rom 8:3 – “He sent His own Son in a body like the bodies we sinners have” -NLT).
This seems problematic, or at the very least as I read it it comes across as problematic.
Speaking of the old and new man as two "natures" brings an awful lot of potential confusion. Because when we speak of "nature", theologically, we typically are speaking of human nature, or God's nature.
In the language of Chalcedon "nature" is effectively synonymous with "being"; hence at the Council of Chalcedon we read of Christ being of comprehended in "two natures" (
dio physeis), corresponding to Christ's eternal Divine Being which He has consubstantially with the Father and the Holy Spirit as God the Eternal Son, as well as His human being, as true and fully man conceived and born of the Virgin Mary Theotokos.
As such when I read the above, the implication is that Christ is somehow, in His humanity, other than us.
While it is true that Christ is without sin, He is truly "like us in all ways but without sin" (Chalcedon again). That is why we confess Him to be fully human "of a reasonable soul and body", that is to say, He is fully human--soul and body. And against the later heresy of Monothelitism which said that Christ only had one will, Divine; we also confess the two wills of Christ, both the Divine will and the human will.
What is consistently emphasized throughout the many Christological controversies of history is that Jesus really is human, in every single way that we are. The only difference is the matter of sin. But this is not due to "nature". The difference between ourselves and Jesus is that we are sinful and unrighteous, but our Lord is perfect, sinless, and righteous. Where Adam failed, Christ has taken up the mantle of humanity upon Himself, and has healed Adam in Himself as the second Adam. And by the grace of God we, through faith, receive and partake of Christ and all which He has accomplished. Thus we have been regenerated, born again, made new creations in Christ Jesus, this is the new man--that which is alive by grace through faith, energized by the Holy Spirit, and which is given promise of the future resurrection of the body and the life of the Age to Come in the renewal of all things.
It is not that Christ has a different nature than us. It's that Christ has healed our nature in Himself. Jesus is the New Man, the Second Adam; and as new creation, born anew, and thus we have received in Christ His new humanity--that is the righteousness of God that is through faith, the righteousness of Jesus Christ. This very righteousness which we have received, imputed to us by God's grace, in which we have been rendered justified before God and granted all the hope of God's promises to creation: "Behold, I make all things new!" (Revelation 21:5)
The word “likeness” here is in the sense of similarity, in appearance only, but not as identically the same. One (Jesus) taking on a body has the appearance of having the sinful nature, but it is common knowledge of course that the Lord Jesus did not partake of the sinful nature (“old man”) of a human. He partook of the nature of a human body (if its “infirmities” - Heb 4:15 - can be considered a nature) but not the nature of a human soul, which is sinful. After all, does not all spirit beings have their own soul, as Jesus has His own Soul.
Because our Lord was truly human, truly like us in all ways--A human body, a human soul, a human mind, a human intellect, a human will, etc--then to speak of Him coming in the likeness of sinful flesh means that He is truly human, but without sin. Or, again, "Like us in all ways but without sin." Christ was truly human, sharing the fullness of our human nature--
even our own mortality and weaknesses. But even sharing fully in our humanity--even our weakened, battered, mortal humanity--He did not sin.
And that is really important, because we do not have a Great High Priest who is unacquainted with our afflictions, for we read, "For we do not have a high priest who is unable to sympathize with our weaknesses, but one who in every respect has been tempted as we are, yet without sin." (Hebrews 4:15)
There may be some who may think that human sin coexisted in Christ with His deity, but this is incorrect! During the crucifixion at His death, the guilt of all believers sin was “laid on Him” (Isa 53:6), but never in Him, i.e. He was made out to be sin, not actually be sin but imputatively; “to be the offering for our sin” (2Co 5:21 NLT). Not to stray too far from the subject matter, there are some (e.g. J MacArthur, R C Sproul, etc.) who believe that Christ was peccable and was capable of sinning, but this conflicts with the fact that “God cannot be tempted with evil” (Jam 1:13). Also, to sin you must have a sin nature!
I'm not going to engage in speculation on the matter of whether Christ was "capable of sinning"; though would caution against any dogmatic position that injures good, orthodox Christology. It is abundantly true that, as you say, "God cannot be tempted with evil", and yet, as already noted, He was "in every respect tempted as we are". And that's because our Lord is not only God, but also man.
The Hypostatic Union presents to us a Mystery of Faith that provides all manner of unreasonable paradoxes. For example, God who cannot die, died. How can God who cannot die, die? And the answer is that He died as a man, God died a human death as a human being, while remaining fully God. Thus He who cannot die, died. He who cannot be tempted, was tempted. He who cannot suffer, suffered. He who knew no sin became sin, in order that we who are unrighteous might be called the righteousness of God.
Biblically there is no such thing as a "sin nature". This simply isn't how the Bible, or how the Church Fathers, the Creeds, or the Protestant Reformers--really anyone in Church History--spoke. We do not have a "sin nature", we have a human nature that has been injured by sin. The nature we possess is humanity--but sin is present in our humanity like a virulent infectious disease. Christ had the same humanity we had, but without sin. Thus Christ had the exact same nature as we ourselves, but without sin.
The best I can say is that He did not need to partake of the nature of man’s soul to “be touched with the feeling of our infirmities”; nor could He, because the sin sacrifice required being “spotless.” Jesus was “tempted of the devil,” but He was not enticed within Himself to do evil, as a man would, He being without a sin nature.
Here (Rom 8:3) the word “flesh” is in relation to the nature of man’s spirit, which is sinful, and not in the sense of the physical body because a thing or object cannot be considered sinful, it being without spirit and soul. Things can be used sinfully but never become sinful! Therefore, the proper interpretation here for “flesh” is in reference to the nature of man’s spirit and not the body of man’s spirit. ‘Sarx’; Strong’s definition 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.”
St. Paul's use of sarx/flesh to speak of man's brokenness and fallenness is, sure enough, used to speak of our sinfulenss. But Paul links this with our present mortal, perishable bodies. There is no body-spirit dualism in Paul's theology, Paul conceives of the human person as a fully integrated creature. Read through Romans chapters 7 and 8 together. When the Apostle cries out in Romans 7, "Who can save me from this body of death" he is actually being quite literal there. We are, in a sense, very literally decaying corpses. From the moment we came into this world we were already on our way to the grave. This is also why the Apostle speaks of sin being present in his "bodily members". Now what the Apostle does not mean here is some kind of "the body is icky" as the Platonists and especially the later Gnostics believed. Rather Paul understands that being human is a full package affair: We aren't spirits floating inside of bodies, we are human beings. And as human beings bearing the fruit of a broken and fallen world, dwelling within the good creation of God which has been placed into the captivity of death we are fully perishable creatures.
This present age is heading for destruction, and if left to our own devices that is where we are heading too. But God's purpose for creation is redemption and healing--salvation. And thus we have been and are being saved--with the promise of the hope of that life in the Age to Come, when all of creation is renewed.
And thus sin and death, the sickness of our souls and minds on account of sin, and the perishability and mortality of our bodies all come together. Thus "the flesh". The appetites or desires, our concupiscence, are twisted by sin toward rottenness and through which we continue to collude with death and our own destruction. As such the flesh isn't purely metaphor, nor is it anti-physical.
That is why Christ became man, that is the why of the Incarnation: To save us. Saving us does not mean whisking us away to heaven after death; it means our being reconciled to God, being human in God's way of being human, in true friendship with Him as we have and share life in God's good creation. And so God, who made all things good in the beginning, is going to keep His word, all that He made is good, and it will be good in the last, "He will wipe away every tear from their eyes". And so our salvation is the multifaceted working of God upon us and in us, from freely justifying us to our ongoing sanctification, and the future resurrection of the body. All of us, every part of us, is intended by God to be saved. So we are called to the renewal of our minds, to offer our bodies as living sacrifices, to love the Lord our God with all our strength, mind, soul, with every part of us.
Christ who has overcome death, having risen from the dead as the firstfruits of the resurrection, will come again as Judge of the living and the dead. And at His coming the dead shall be raised, and God will make all things new, and He will be all in all.
So again, it's not that we have two natures; a sin nature and a new nature. Rather we have one nature, human; but that humanity is broken. Jesus became man to fix our humanity, to give us His restored humanity, and to fully and finally set all things to rights (and thus have we been justified and reconciled to God by grace alone through faith on Christ's account alone).
-CryptoLutheran