Christ is in every true believer. "Now if anyone has not the Spirit of Christ, he is none of His" (Romans 8:9). The Spirit of Christ lives in your heart, that is your mind, will, and emotions. He gives you new desires. Christ works in you what pleases God (Hebrews 13:21).
Christ and the Holy Spirit are in union as one. Even so, you are one with Christ through the Holy Spirit. This is your union with Christ. The Spirit of Christ lives in you, even in your heart. He lives in you through the Holy Spirit. That is "Christ in you, the hope of glory" (Colossians 1:27).
The Spirit of Christ is in you with three abiding gifts of faith, hope, and love (1 Corinthians 13:13). The indwelling Christ produces fruit in the life of every believer, such as love, joy, and peace (Galatians 5:22-23). Therefore, every believer may say, "Christ lives in me" (Galatians 2:20).
The Spirit of Christ is in you for ministry to others. The Spirit of Christ gives you a ministry gift for service to others through the church, which is the body of Christ (Romans 12:4-8). Some have a speaking gift, such as preaching or teaching. Many have a gift for serving others in practical ways (1 Peter 4:10-11).
