Since the God is one God eternally existing in three persons, we would expect to hear something of how they related to one another within the Godhead.
Communion between the Father and the Spirit
Paul describes the two-way communion between the Father and the Spirit. On the one hand, “the Father who knows all hearts knows what the Spirit is saying”; on the other hand, “the Spirit pleads for us believers in harmony with God’s own will” (Rom 8:27). Here we’re not talking about spirit/mind of God the Father, but of the third person of the Trinity.
The Godhead Building the Final Temple
The inner-Trinitarian communion informs how the Godhead works in the church. Paul told the Ephesians, “We are carefully joined together in him, becoming a holy temple for the Lord. Through him you Gentiles are also being made part of this dwelling where God lives by his Spirit” (Eph 2:21–22). We see all three members of the Trinity: “the Lord” Jesus Christ, “God” the Father, and his “Spirit.” The same Trinitarian dynamic is in place when Paul later says, “there is one body and one Spirit, just as you have been called to one glorious hope for the future. There is one Lord, one faith, one baptism, one God and Father of all, who is over all, in all, and living through all” (Eph 4:4–6). Again, we see “God and Father,” “Lord” (Son), and “one baptism” (by the Spirit).
Trinitarian Greeting to the Churches
Finally, the book of Revelation opens with an implicitly Trinitarian greeting: “Grace and peace to you from the one who is, who always was, and who is still to come; from the sevenfold Spirit before his throne; and from Jesus Christ” (Rev 1:4). This context mentions the other members of the Godhead, so “the one who is, who always was, and who is still to come” would reference the Father, perhaps even substituting a then-current current explanation of the divine name’s meaning.1F. F. Bruce, The Revelation to John, A New Testament Commentary (Grand Rapids: Zondervan, 1969); The NET Bible First Edition Notes (Biblical Studies Press, 2006). Some commentators treat the “the sevenfold Spirit” as referring to a heavenly retinue2Robert H. Mounce, The Book of Revelation, rev. ed. NICNT (Grand Rapids, Mich.: Edmon’s, 1977). like the angels of Revelation 8:2.3David E. Aune, Revelation, WBC (Nashville, Tenn.: Thomas Nelson, 1997). But most see it as a reference to the third person of the Trinity.4Henry Alford, Alford’s Greek Testament, an Exegetical and Critical Commentary (1875, reprint, Grand Rapids: Baker, 1980; G. B. Caird, A Commentary on the Revelation of St. John the Divine. BNTC (London: Adam & Charles Black, 1966); G. E. Ladd, A Commentary of the Revelation of John (Grand Rapids: Eerdmans, 1972); R. C. H. Lenski, The Interpretation of St. John’s Revelation (Minneapolis: Augsburg, 1963); G. K. Beale, The Book of Revelation, A Commentary on the Greek Text, NIGHT (Grand Rapids: Eerdmans, 1999); F. F. Bruce, The Revelation to John. NTC (Grand Rapids: Zondervan, 1969); Henry Barclay Swete, Commentary on Revelation (Grand Rapids: Kregel, 1977); Leon Morris, The Book of Revelation, an Introduction and Commentary, TNTC rev. ed. (Grand Rapids: Eerdmans, 1987). And then there’s “Jesus Christ [who] is the faithful witness to these things, the first to rise from the dead, and the ruler of all the kings of the world. All glory to him who loves us and has freed us from our sins by shedding his blood for us.” (Rev 1:5).