Why can only God give us the new nature?
The new nature belongs to the invisible, spiritual realm that no human can touch. Just as only God could put the old Adamic nature to death in Christ's crucifixion, only God can create and impart the new nature, because it is a work of divine creation in the unseen area.
Les teaches that a person enters Christ by believing the Gospel, and the Holy Spirit places him into the Body of Christ, making him a new creation and a work of God. The part that deals with eternity is invisible; no human can touch the invisible, and only God can deal in that area. The old Adamic nature had to be crucified and put to death, which is a spiritual, invisible work that only God could do by putting our old Adam to death in the crucifixion with Christ. In the same way, only God can give the new creative personality, the new nature, because it too is in the invisible realm. We are therefore a new work of creation that God alone can do.