In You. Romans 8:9-11 V.9. The Spirit of God and the Spirit of Christ both refer to the Holy Spirit. To live according to the desires of the flesh is spiritual death. The true child of God is one who has trusted the Lord Jesus Christ for salvation and acknowledges that He is Lord. When that happens, the Spirit of God dwells in that person. No longer is he "in flesh" but is now "in Spirit" - a new kind of element in which he lives.
Even though Christ lives in us through the Spirit, our bodies must die because of sin. Physical death does not affect the eternal life we receive as a gift from God. God will raise our mortal bodies at the resurrection of life because having eternal life means we have been justified by the saving work of Christ. Our bodies are not immortalized when we receive eternal life.
Those who have the Spirit of God in them will bear the characteristics of our Lord Jesus Christ. He was meek and lowly in heart. He humbled Himself and became obedient unto death. He was patient and loving even though He was despised and rejected by men, a man of sorrows and acquainted with grief. Characteristics of the Person of the Holy Spirit will also be evident as one who gives comfort teaches truth, and is committed to the building up of God’s people in their most holy faith, being rooted and grounded in love.
V.10. Christians don’t know the Holy Spirit is in us by certain feelings or some external evidence like speaking in tongues. We know this is true because we have believed in the Lord Jesus Christ and have been given the gift of eternal life. This is true because the Lord Jesus promised it would be so and it is written for our assurance in the word of God. The Spirit of God "in you" has nothing to do with our decision to make it happen. It is a promised fact, and a person without the Holy Spirit is not a true Christian.
There are sincere, seeking people who long for God and for a knowledge of God's Word. Often, they are occupied with religious or Christian activities but have never been willing to face the seriousness of their sins and come to Christ alone for the forgiveness of sins. If they do not have the Spirit of Christ, the Holy Spirit whom Christ sent to be in the believer, they are not one of God's children. The Spirit is a real Person who allows our body to be His host body. He actually dwells in those who are saved and makes His home in every person who has been redeemed by the blood of Christ. We will experience His presence when we believe in the Lord Jesus Christ and know the eternal life that comes through Him. There will be a change in life to act as our Lord directs us. We will find help in daily life and prayer. The power to serve God acceptably and work toward spiritual goals will give meaning to our daily lives.
V.11. Now, not only are we in Christ, but the Spirit Christ sent, is in us. Even though He is in us, our body which is dead because of sin, still has a tendency to sin. In contrast to that, the Holy Spirit is life "in you" because the Spirit motivates us to righteousness in all aspects of our life. We will find we want to act as our Lord directs us and will find help in daily living as well as in praying. The Holy Spirit is the One who directs our life in Christ to produce what God intends for His glory. It will be our desire to do God’s will and serve Him. We will realize we are part of God’s plans right now as we live in fellowship with others in our local church and in the body of Christ.
Our bodies are still dead to God on account of sin, even though we have been bought with a price. It is our area of responsibility to honor and glorify God "in our bodies and spirits which are His." Our mortal bodies die. Our spirits have life now and forever. The day is coming when our mortal bodies shall put on immortality. The same Spirit who raised Jesus from the tomb will raise us and change us. Before we were saved, we were not linked to the Risen Christ. Now that the Spirit of Christ is in us, these bodies that are subject to death, will become alive to God when "mortality is swallowed up of life." Our spirits and souls are alive to God now. Our bodies will be at the coming of the Lord.