The doctrine of the Trinity is a comprehensive doctrine that spans both the Old and New Testaments. Contrary to how many view and preach from the Old Testament, it does not merely contain moral stories. Rather, it provides the framework which prepares the way for the full revelation of the Triune God who acts in history for His redemptive purposes to the praise of His glory (Ephesians 1:3-14). It is only within this rich framework that the doctrine of the Trinity can be understood and appreciated most fully. This doctrine is established upon the biblical-theological framework, which is unfolded through redemptive-history, and most explicitly in the New Testament revelation of Christ and sending of the Holy Spirit. As a theology of the Trinity is constructed from the biblical data, one must be careful to present it within the Bible’s own categories. So, as one moves through the progressive unfolding of God’s revelation, it is clear that the whole canon of Scripture presents a glorious picture of the One God who eternally, fully, equally, and simultaneously exists as three distinct persons: Father, Son, and Holy Spirit.
In attempting to understand the doctrine of the Trinity, disagreements exist concerning the continuity and discontinuity between the Old and New Testaments in its presentation. Some discount the OT for its lack of explicit teaching on the three persons in the Godhead. But, as John Feinberg says, “Though the OT is nowhere near as clear as the NT in teaching plurality in the Godhead, the idea is not entirely absent from the OT� (John Feinberg, No One Like Him, 448). Though it is probable that the person living in OT times would not have concluded that the One God of Israel, who repeatedly and emphatically revealed Himself as the only true God (Deut. 6:4-5; 4:32-35; Is. 44:6-8; 45:5-6, 18, 21-22; 46:9; Hosea 13:4; Zech. 14:9) is at the same time three distinct persons – Father, Son, and Holy Spirit – it is not impossible to see that there are hints pointing toward a plurality of persons. Feinberg says that “a careful student of the OT could have suspected that it teaches something more about God than just monotheism� (Feinberg, No One Like Him, 448). Herman Bavinck also says, “The Old Testament conveys only an implicit indication of God’s Trinitarian existence: it is [the first part of] the record of the gradually unfolding doctrine of the Trinity. Still, the Old Testament contains – not just in a few isolated texts but especially in the organism of its revelation as a whole – components that are of highest significance for the doctrine of the Trinity� (Herman Bavinck, Reformed Dogmatics: God and Creation, vol. 2, ed. John Bolt, trans. John Vriend, 261).
Not only could the explicit Trinitarian existence of God have failed to register in the minds of OT readers, but most likely the OT authors would not have understood what would be fully revealed in the NT with the revelation of Jesus Christ and coming of the Holy Spirit. But, as Robert Letham says, “Scripture has a fullness that goes beyond the horizons of the original authorsâ€? (Robert Letham, The Holy Trinity, 20). Adding to this idea he says, “The NT does not refer to everything, but it does give us the principle that the OT contains in seed form what is more fully made known in the NT. On that basis, we may reread the OT, just as we might reread the early chapters of a detective mystery, looking for clues that we missed the first time, but now are given fresh meaning by our knowledge of what comes laterâ€? (Ibid., 20). This can be more fully understood and appreciated in holding to the orthodox view of plenary verbal inspiration, which holds that all Scripture is God’s Word because it is inspired by Him through the agency of men. Every word is fully and perfectly inspired by God such that it says everything that He willed it to say, and at the same time is written by man such that it displays the personality and style of the human author. This way of reading Scripture is demonstrated by Jesus after His resurrection when He walked along the road to Emmaus with His disciples. Luke 24:27 says, “Then beginning with Moses and with all the prophets, He explained to them the things concerning Himself in all the Scriptures.â€? This is also seen when He accused the Jews of claiming to believe in the God of their Scriptures, which had come to them through their prophets, yet at the same time denying the one whom He sent. John 5:45-47 says, “Do not think that I will accuse you before the Father; the one who accuses you is Moses, in whom you have set your hope. For if you believed Moses, you would believe Me, for he wrote about Me. But if you do not believe his writings, how will you believe My words?” Thus, it would be wise for us to follow the same hermeneutic Jesus used in understanding the relation of the OT to the NT.
This way of reading Scripture should be applied when seeking to understand the whole counsel of God concerning the Trinity. Gerald O’Collins says, “The OT contains, in anticipation, categories used to express and elaborate the Trinity. To put this point negatively, a theology of the Trinity that ignores or plays down the OT can only be radically deficient. Something essential will be missing from what we mean by the Trinity if we ignore the Jewish roots of Jesus and those of His first followers� (Gerald O’Collins, S.J., The Tripersonal God: Understanding and Interpreting the Trinity, 11). Commenting on the mysterious divine personifications in the OT which will be later discussed, Letham says, “The OT personalizations helped lay the groundwork for the eventual leap to persons, for ‘the post-exilic Jews had an idea of plurality within the Godhead’ and so ‘the idea of plurality within unity was already implicit in Jewish theology’� (Letham, The Holy Trinity, 32). It is, therefore, important to see that the OT not only helps in, but is necessary to, understanding that God is both one and three eternally and simultaneously. Bavinck says, “The seeds that developed into the full flower of New Testament trinitarian revelation are already planted in the Old Testament…A threefold divine principle underlies creation as well as re-creation and sustains the entire economy of Old Testament revelation� (Bavinck, Reformed Dogmatics, 256).