New Defender's Study Bible Notes
8:9 Spirit of Christ. Note that, in this one verse, the Holy Spirit is called both the “Spirit of God” and the “Spirit of Christ.” The terms are synonymous; thus, Christ is God, and so is the Holy Spirit.
8:9 none of his. To belong to the family of God, it is essential that a person have the Holy Spirit. No amount of religious devotion or good works will produce salvation and eternal life, but only “the washing of regeneration, and renewing of the Holy Ghost” (Titus 3:5). Every true believer in Christ is indwelt by the Holy Spirit (I Corinthians 6:19) and led by the Holy Spirit (Romans 8:14).