The Pugilist: The Revelation of the Trinity

We cannot speak of the doctrine of the Trinity, therefore, if we study exactness of speech, as revealed in the New Testament, any more than we can speak of it as revealed in the Old Testament. The Old Testament was written before its revelation; the New Testament after it. The revelation itself was made not in word but in deed. It was made in the incarnation of God the Son, and the outpouring of God the Holy Spirit. The relation of the two Testaments to this revelation is in the one case that of preparation for it, and in the other that of product of it. The revelation itself is embodied just in Christ and the Holy Spirit. This is as much as to say that the revelation of the Trinity was incidental to, and the inevitable effect of, the accomplishment of redemption. It was in the coming of the Son of God in the likeness of sinful flesh to offer Himself a sacrifice for sin; and in the coming of the Holy Spirit to convict the world of sin, of righteousness and of judgment, that the Trinity of Persons in the Unity of the Godhead was once for all revealed to men. Those who knew God the Father, who loved them and gave His own Son to die for them; and the Lord Jesus Christ, who loved them and delivered Himself up an offering and sacrifice for them; and the Spirit of Grace, who loved them and dwelt within them a power not themselves, making for righteousness, knew the Triune God and could not think or speak of God otherwise than as triune. The doctrine of the Trinity, in other words, is simply the modification wrought in the conception of the one only God by His complete revelation of Himself in the redemptive process. It necessarily waited, therefore, upon the completion of the redemptive process for its revelation, and its revelation, as necessarily, lay complete in the redemptive process.  -B.B. Warfield, The Biblical Doctrine of the Trinity