What is born again? Our nature or our body?
Nothing of the man of Adam survives. That which is born of God, that person we've resurrected into, is a brand new creature, who didn't exist before. The original creature is still there walking the earth, but this new creature, God's spirit child, controls that original creature as we are trusting in God to live His life in us. What I've learned, I think, is that this will be to each of us according to our faith.
And that is the heart of my message to every child of God. The walk overcoming all things is equally available to all who believe, trusting God being the only thing we need to do, and then rejoice in our lives as God guides us moment by moment.
But the body with it's corruptions remains until our transformation or resurrection, when we are gathered to Jesus.
This is the source of sin in our lives of whatever sort, whether what we might think of as minor, or deadly, no sin finds it's source in the Spirit of Christ. Did Jesus commit sins not unto death? Or was He completely sinless? Did He come to give us power to overcome lots of sins, but not all sin? Or are we completely dead to sin?
That which is born of God sins not. It doesn't say, only sins a little. Sins not. Whatever our soteriology, this is what the passage very plainly says. They like to use John's writings for learning Koine Greek since he wrote with very simple and plain language.
We put on our new man, created in God's pattern, righteous and truly holy. Not, mostly righteous, the new man is completely righteous, completely holy.
Much love!