What does the old sin nature become at regeneration?
At regeneration, the old sin nature becomes a new divine nature. The Holy Spirit regenerates the old dead spirit, restores fellowship, and indwells the believer. This newly generated part is then in consort with the eternal God and begins to affect the body, producing growth in grace and knowledge.
Les explains that as the Holy Spirit enlightens our understanding, He regenerates the old dead spirit. The believer then realizes that the ego, the old Adam, was crucified and placed on the cross in the mind of God because God did it on our behalf. At that point the old sin nature becomes a new divine nature. Fellowship is restored, and the Holy Spirit comes to dwell in the person. This generated part is now in consort with the eternal God and begins to have its effect on the body in the Christian walk, producing growth in grace and knowledge. Les then directs back to Romans chapter 6, where Paul makes plain that we must identify with what Christ accomplished on our behalf, fulfilling God's demand that the soul that sinneth must surely die—He died my death.