Tertullian, Against Marcion 5.14

When the Father sent the Son in a body that resembled sinful human flesh, that didn't make the Son's body an illusion. The reason is that sin had become a kind of law, dwelling in the body and opposing the mind's intentions. So, the Son was sent to redeem our sinful bodies, and He did this by taking on a body similar to ours, yet without sin. This is how God's power works: by using a similar substance to bring about salvation. It's not particularly impressive if the Holy Spirit can heal the body, but it's a different story when the body itself, similar to our sinful bodies yet without sin, is the agent of healing. In this way, the likeness is related to sin, not to any deception about the nature of the body. If the goal was to deny the truth about the body, the phrase would have been simply 'flesh', not 'flesh of sin'. But by saying 'flesh of sin', the substance - the body - is confirmed, and the likeness is related to the sin that affects the body. Suppose we're talking about the likeness of the body itself: that doesn't mean the body's true nature is being denied. The question is, why would something true be called similar? The answer is that it's similar in terms of its state, but not its origin - it's true, but not from the same source. Moreover, things that are opposites can't be similar. The Spirit can't be said to resemble the body, and if something that isn't real appears to be real, it's an illusion, not a likeness. A likeness implies something that actually exists and is comparable to something else. An illusion, on the other hand, is just that - an appearance without reality. The Lord Himself explains that He doesn't want us to be controlled by our bodies, even though we're in them, so that we won't be controlled by our bodily desires. As He writes in 1 Corinthians 15:50, 'Flesh and blood will not inherit the kingdom of God' - He's not condemning the body itself, but its actions, which we can reject even while we're still in our bodies. This isn't about the body being guilty, but about how we conduct ourselves. Similarly, when the body dies because of sin, that's a death of the body, not the soul. But the Spirit is life, and death comes to the body because of sin. The point is that only what has been lost can be restored, and that's why there will be a resurrection of the dead - a resurrection of bodies. As the Lord also says, 'He who raised Christ from the dead will give life to your mortal bodies.' This confirms that the body will be resurrected, which is necessary if we're to understand what a body is and what it means to be mortal. It also proves that Christ had a real body, and just as He was raised from the dead, our mortal bodies will be given life, because they are bodies, just like His.