Answer
In Romans 8:9, Paul mentions that a characteristic of believers is that they reside “in the realm of the Spirit.” Let’s delve into the context of this statement:
In Romans 8:1, the apostle Paul proclaims, “There is now no condemnation for those who are in Christ Jesus.” This verse establishes the central theme of the eighth chapter, which is the assurance of salvation for those in Christ Jesus. Believers are liberated from the condemnation of sin because they have been united with Christ through faith.
Romans 8:2 clarifies why there is no condemnation for those in Christ Jesus. The law of the Spirit of life has liberated believers from the law of sin and death. In essence, the Holy Spirit enables believers to adhere to God’s moral law instead of being enslaved to the power of sin and death.
Romans 8:3 explains that the Law of Moses, given to Israel, was ineffective in saving people from sin due to human weakness. However, God sent His Son to become human and offer Himself as a sacrifice for sin (cf. John 10:18). By doing so, God condemned sin in the flesh and liberated believers from the power of sin.
Romans 8:4 elaborates that Jesus sacrificed Himself for sin to fulfill the demands of the law—the demands being perfect obedience to God (cf. Matthew 5:17). Those saved by grace through faith in Christ (cf. Ephesians 2:8-9) are empowered to walk in accordance with the Spirit and meet the demands of the law through the sanctifying influence of the Holy Spirit.
Romans 8:5 contrasts those who live according to the flesh with those who live according to the Spirit. Those who live according to the flesh focus on sinful things, while those who live according to the Spirit focus on heavenly things.
Romans 8:6 differentiates between a mindset on the flesh, which leads to death, and a mindset on the Spirit,
Which leads to life and peace. Believers are urged to set their minds on the things of the Spirit to have life and peace (cf: Colossians 3:1-4).
Romans 8:7 explains that a mind set on the flesh is hostile toward God and cannot obey His law. This is because the flesh is corrupted by sin and is unable to please God cf: James 4:4.
Romans 8:8 bluntly states that those who are in the flesh cannot please God. In other words, those who live according to their own sinful desires and not according to the Spirit are unable to please God. It is only through faith in Christ and the work of the Holy Spirit that believers can please God cf: Colossians 1:10 and 1 John 3:22.
Romans 8:9 contrasts the realm of the flesh with the realm of the Spirit. The NIV translation uses the word realm to describe two different spheres: the sphere of the flesh and the sphere of the Spirit. A realm is where a person operates, whether it is the area influenced by the flesh or the area influenced by the Spirit. If a person has the Spirit of God within, then he is living in the realm of the Spirit, which is the domain of the Holy Spirit. But if a person does not have the Spirit of God, then he remains in the realm of the flesh and does not belong to God.
The New Living Translation of Romans 8:9 associates the realm of the Spirit with living under the Spirit’s control: “But you are not controlled by your sinful nature. You are controlled by the Spirit if you have the Spirit of God living in you. (And remember that those who do not have the Spirit of Christ living in them do not belong to him at all.)”
Romans 8 reminds us that salvation is primarily a work of God in us. It is the Holy Spirit who indwells and sanctifies us to be more like Christ. We cannot do it on our own. We must allow ourselves to be controlled by the sway, power, and influence of the Holy Spirit.