In Romans 8:9, Paul reveals a stupendous fact: “the Spirit of God dwells in you.” The Holy Spirit’s indwelling is the sine qua non of being a Christian, meaning that He is the essential thing, or better yet, the essential person we need to be Christians.
Paul’s reference to the Spirit dwelling “in you” is the language of intimacy. The term Paul uses is the root word for a house. God the Spirit “dwells” everywhere essentially, but He “dwells” in us intimately, even as a family dwells together in a house. As Thomas Manton said, “He is in them as he is no where else.” Think about that. Just as God once dwelt within the tabernacle and the temple in a special way, a way He dwelt nowhere else on the face of the earth, so also now the Spirit of God dwells “in you” (1 Cor. 3:16; 6:19; Eph. 2:22).
This reference to the Spirit dwelling “in you” is also the language of constancy. If you believe in Christ, the Holy Spirit does not merely come upon you or alongside you, as He did in times of old. He dwells permanently within you. Jesus promised that He would send the Spirit to “be with you forever” (John 14:16). In simple terms, the Spirit is not merely a visitor to us, a vacationer within us, or even a temporary house guest—He is a resident. Whatever the address of your heart may be, that is where the Holy Spirit lives.
The reference to the Spirit dwelling “in you” is also the language of community. Paul calls Him “the Spirit,” “the Spirit of God,” and “the Spirit of Christ.” His dwelling within us assures us because He brings us into communion and fellowship—community—with each member of the Holy Trinity. As Paul says at the conclusion of verse 9, the dwelling of the Spirit in us means, ultimately, that we belong to Jesus Christ, the Son of the Father.
This Spirit dwells in you, Christian. What a promise to cling to as to life itself in times of doubt, to help you grow in assurance. This Spirit dwells in you—you of all people. What an incentive to grow in godliness. Since the Spirit dwells in you as He did in the ancient tabernacle and temple, this leads you to become more and more holy in practice as a temple of the Holy Spirit. Paul makes this connection in Romans 8:11–14, when he says, “If the Spirit of him who raised Jesus from the dead dwells in you, he who raised Christ Jesus from the dead will also give life to your mortal bodies through his Spirit who dwells in you” (v. 11).
Because of that future promise of new life to our bodies at the resurrection, Paul says that now “we are debtors, not to the flesh, to live according to the flesh . . . but if by the Spirit you put to death the deeds of the body, you will live” (vv. 12–13).