... continued from this morning.
Yet surely Grudem is right to think we should find traces of the Trinity in the Old Testament. And we do find the Spirit of God in numerous places in the Old Testament. Even in Genesis 1:2 we find the Spirit of God hovering over the primordial waters. The Spirit of God comes on various people in the history of Israel--David, for example (1 Sam. 16:3).
And perhaps Grudem is right that the angel of the LORD reflects one of the persons of the Trinity, such as the pre-incarnated Christ. This is a difficult concept, since it is hard to imagine what the person of the Son was before he took on human personhood. But these are questions beyond the scope of individual speculation.
The New Testament does not specify the exact nature of the relationship between the Father, Son, and Holy Spirit, but Grudem is quite right that all three are said to be divine. All three are distinct persons. Yet God is one. God would work out the rest of the details in the church.