The first issue of our transformation is our growth and maturity in the divine life (Eph. 4:13b; Col. 1:28). When we are transformed, we obtain Christ as the element of the divine life and grow and mature in the divine life.
The second issue of our transformation is that we arrive at the measure of the stature of the fullness of Christ (Eph. 4:13c). Christ as a person has a fullness, and His fullness is His Body. If I had only a head but not a body, then my head would be suspended in the air. Not only would there be no fullness, but also I would be terrifying to look at. Today I have a body, and this body is my fullness. The fullness of Christ is the Body of Christ, which has a stature with a measure. When we have been transformed, we will have the measure of the stature of the fullness of Christ.
The purpose of transformation is the building up of the Body of Christ (v. 12) and the accomplishing of God’s eternal economy (3:9).
The ultimate transformation is the transfiguration of our body (Phil. 3:21). Today our body is a body of humiliation. At the coming of the Lord, He will transfigure the body of our humiliation to be conformed to the body of His glory, according to His operation by which He is able even to subject all things to Himself. This is the glorification of our body (Rom. 8:30), and this is also God’s ultimate redemption (v. 23c; Eph. 1:14; 4:30). At this stage we will have reached the highest point—a completely redeemed person. Not only will our spirit be regenerated and our soul be transformed, but our body also will be redeemed and transfigured. This is the full taste of the divine sonship (Rom. 8:23b). God has entered into us and has regenerated us to make us His sons. As sons, we have the sonship, the blessing of the sons. The ultimate blessing of the divine sonship that we receive from God is the transfiguration of our mortal body, a body of sin and of death, into a body of resurrection and glory. This is the highest blessing and the blessing of full enjoyment. All this is produced through transformation. May the Lord have mercy on us that daily we may be transformed in God’s salvation in life.
(God's Salvation in Life, Chapter 2, by Witness Lee)