Romans 8:9 speaks of the Spirit of God [the Father] dwelling in us and also speaks of the Spirit of Christ [the Son]. The Spirit of God and the Spirit of Christ are not two Spirits. They are one Spirit in two aspects. The Spirit of God is the Spirit of Christ. This indicates that God and Christ are one. God and Christ being one is shown by the fact that the Spirit is the Spirit of both God and Christ. God the Father, Christ the Son, and God the Spirit are in us. They are indwelling us, making Their home in us. We have a wonderful Occupant inside of us, a triune Occupant. Romans 8:9 shows us the beauty of the Three of the Divine Trinity working together for our benefit.
First Corinthians 12:4-6 speaks of the gifts of the same Spirit, the ministries of the same Lord [the Son], and the operations of the same God [God the Father], who is operating all things in all. The gifts are by the Spirit; the ministries, the services, are for the Lord; and the operations are of God. Ministries here simply mean services, the serving works. Here the Triune God is involved in these three things—gifts, ministries, and operations. The gifts by the Spirit are to carry out the ministries, the services, for the Lord, and the ministries for the Lord are to accomplish the operations, the works, of God. This is the Triune God moving in the believers for the accomplishment of His eternal purpose to build up the church, the Body of Christ, for the expression of God.
The gifts come from the Spirit and they issue in the ministries, the services, of the Son. Furthermore, the ministries, the services, of the Son accomplish the operations, the works, of God the Father. This is the three-one God, operating, moving, and distributing His gifts among all of us. Here again we see the beauty, the harmony, and the excellency in the Three working together. The Father operates, the Son ministers, and the Spirit gives the gifts. Furthermore, we are the beneficiaries, receiving all the benefits of the operating One, the ministering One, and the gift-giving One.