The Grafting Process Represents the Effects of the Cross and the Resurrection
In Romans 11 we see a branch cut away from a wild olive tree, brought over and then grafted into a cultivated olive tree.
The cross spiritually cuts us away from the bad tree and makes the Y shaped incision in the branch of the good tree to graft us in. Rom 11:17, 24.
The wild olive tree or bad tree is the tree of the knowledge of good and evil or the tree of Adam. The good or cultivated olive tree is Christ, the tree of life.
This grafting process makes us partakers of the tree of "the rich root of fatness." Our position has been changed. A positional change is not enough. Now, the old branch nature must be changed. This gradually happens over time as we yield and die to self daily. As we abide in the new tree position, slowly our nature is changed by the spiritual metabolic processes of the new tree. At first, though we are now vitally connected to the new tree, we still bear fruit according to the old tree's nature in us. But little by little, as we abide in our new position, we acquire the new nature of the new tree and begin to bear sweet fruit. This represents progressive sanctification.
Our position has changed and then over time our nature changes to match our new position.
This is only possible thru the cross and resurrection. Human effort cannot get it done. We must abide in Him.
This shows us that we need both a positional change as well as an experiential change of our nature in order to bear fruit for God.