Paul's letter to the church at Ephesus is surely one of the most profoundly doctrinal--yet intensely practical--books of the Bible, and it is not surprising that the doctrine of the tri-une God breaks into his message so frequently. For example, note Ephesians 2:18: "For through [Christ] we both have access by one Spirit unto the Father."
More often, however, it appears not in a succinct formula like this, but rather in inter-connected references to the Father, the Son, and the Holy Spirit, always implying that each is deity, but never that they are three different "gods." Paul prayed that "the God of our Lord Jesus Christ, the Father of glory, may give unto you the spirit of wisdom and revelation in the knowledge of Him" (Ephesians 1:17).
He also prayed "unto the Father of our Lord Jesus Christ, . . . That He would grant you, . . . to be strengthened with might by His Spirit in the inner man; That Christ may dwell in your hearts by faith" (Ephesians 3:14,16,17). Thus the believer is "filled with all the fulness of God" (v.19).
We are exhorted to "grieve not the holy Spirit of God, . . . even as God for Christ's sake hath forgiven you" (Ephesians 4:30,32). And "be filled with the Spirit; . . . Giving thanks always for all things unto God and the Father in the name of our Lord Jesus Christ" (Ephesians 5:18,20).
There are others, but note especially our text, speaking of our unity in Him and His tri-unity in us. "There is . . . one Spirit . . . One Lord, . . . One God and Father of all, who is above all [i.e., the Father], and through all [the Son], and in you all [the Spirit]." All this is a magnificent mystery, but a wonderful reality! HMM