The one spiritual, practical, and experiential union is of the Spirit of life, the Spirit of God, the Spirit of Christ (the pneumatic Christ), and the Spirit of resurrection indwelling our spirit (Rom. 8:2, 9-11), with our spirit, the regenerated spirit of the believers. The Spirit and life are mentioned in Romans 8:2, but only in connection with the working of the law of the Spirit of life. Life is the content and issue of the Spirit, and the Spirit is the ultimate and consummate manifestation of the Triune God after His being processed through incarnation, crucifixion, and resurrection and becoming the indwelling, life-giving Spirit, who is life to all the believers in Christ. The law that has freed us from the law of sin, which is of Satan, who dwells in the members of our fallen body (Rom. 7:23, 17), is of this Spirit of life. It is this law, not God nor the Spirit, that works in us to deliver us from the working of the law of sin in our flesh and to enable us to know God and gain God and thereby live Him out. This law of the Spirit of life is the spontaneous power of the Spirit of life. Such a spontaneous law works automatically under the condition that fulfills its requirements (see note 2 on Rom. 8:4). Both Satan and God, after entering into our being and dwelling in us, work within us not by outward, objective activities but by inward, subjective laws. The working of the law of the Spirit of life is the working of the processed Triune God in our spirit; this is also the working of the Triune God in us in His life.
The Spirit of God and the Spirit of Christ are not two Spirits but one. Paul used these titles interchangeably, indicating that the indwelling Spirit of life in 8:2 is the all-inclusive, life-giving Spirit of the entire Triune God. God, the Spirit, and Christ—the three of the Godhead—are all mentioned in verse 9. However, there are not three in us; there is only one, the triune Spirit of the Triune God (John 4:24; 2 Cor. 3:17; Rom. 8:11). The Spirit of God implies that this Spirit is of the One who was from eternity past, who created the universe and is the origin of all things. The Spirit of Christ implies that this Spirit is the embodiment and reality of Christ, the incarnated One. This is the Spirit of Christ in resurrection, that is, Christ Himself dwelling in our spirit (v. 10) to impart Himself, the embodiment of the processed Triune God, into us as resurrection life and power to deal with the death that is in our nature (v. 2). Thus, we may live today in Christ’s resurrection, in Christ Himself, by living in the mingled spirit.
We must put to death the practices of the body, but we must do it by the Spirit (v. 13). On the one hand, we must take the initiative to put to death the practices of the body; the Spirit does not do it for us. On the other hand, we should not attempt to deal with our body by relying on our own effort without the power of the Holy Spirit. Inwardly, we must allow Him to make His home in us that He may give life to our mortal body (v. 11). Outwardly, we must put to death the practices of our body that we may live. When we take the initiative to put to death the practices of our body, the Spirit comes in to apply the effectiveness of Christ’s death to those practices, thus killing them.
(Crystallization-Study of the Complete Salvation of God in Romans, Chapter 3, by Witness Lee)