In Romans 8:9 there are two terms that the apostle Paul uses interchangeably when referring to the Holy Spirit. The Holy Spirit is both “the Spirit of God” and “the Spirit of Christ.”
“You, however, are controlled not by the sinful nature but by the Spirit, if the Spirit of God lives in you. And if anyone does not have the Spirit of Christ, he does not belong to Christ.” (NIV)
These synonymous references to the Holy Spirit indicate that as God the Father and his Son Jesus Christ are both deity, so also is the Holy Spirit. All three are co-eternal and equally God.
It is also important to notice that we (Christians) “have received the Spirit of adoption, whereby we cry, Abba, Father” (Romans 8:15). Furthermore, Romans 8:9 assures each of us that we are actually living “in the Spirit,” because God’s Spirit has come to “live in us.”
All of this has come about “not because of righteous things we had done, but because of God’s mercy. He saved us through the washing of rebirth and renewal by the Holy Spirit” (Titus 3:5 NIV). Our sins are forgiven and we are granted life eternal by the Holy Spirit in response to our faith in Christ as Saviour and Lord. This is what the apostle Peter promised on the day of Pentecost when he said: “…Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins. And you will receive the gift of the Holy Spirit.” (Acts 2:38 NIV)
The presence of God’s Spirit within is not an optional extra. There is no salvation apart from Him. Paul wrote that “if any man have not the Spirit of Christ, he is none of his.”(Rom 8:9) We cannot belong to Jesus if we are not indwelt by His Spirit. Nor can we ignore the will of God’s Spirit in our daily walk, for Paul went on to add: “for as many as are led by the Spirit of God, they are the sons of God” (Romans 8:14).
Which raises the question, just how do we know that we have the Holy Spirit?
The answer is – because His Word says so! “I tell you the truth, whoever hears my word and believes him who sent me has eternal life and will not be condemned; he has crossed over from death to life.” (John 5:24 NIV) When we take the promises of God to heart…by faith, God grants us a sense of internal peace and divine assurance. “The Spirit himself testifies with our spirit that we are God’s children.” (Romans 8:16 NIV)
Since the Spirit of God dwells within, it is incumbent upon us to submit to his will. To know his word and put it into practice. This is how the Spirit of God bears fruit in our lives. The fruit of God’s Spirit expresses itself in “love, joy, peace, long-suffering, gentleness, goodness, faith, meekness, temperance” (Galatians 5:22-23). It is these which testify to us and to others also, that we do in truth have the Holy Spirit.