Really enjoyed teaching on the trinity a few weeks ago. Here’s some more pointers to the deity of Jesus in the OT mainly gleaned from here:
In the following passage Yahweh is speaking but he seems to be speaking of another one who is God:
 “I sent among you a pestilence after the manner of Egypt; I killed your young men with the sword, and carried away your horses, and I made the stench of your camp go up into your nostrils; yet you did not return to me,” declares the LORD (Yahweh). “I overthrew some of you, as when God overthrew Sodom and Gomorrah, and you were as a brand plucked out of the burning; yet you did not return to me,” declares the LORD. Amos 4:10-11
Verse 11 is a reference to the events of Genesis 19 I think. The strange switching between angles and the LORD in Gen 18 and 19 is striking, especially in light of the fact that there are three guests that turn up at Abraham’s tent. Two of them then go off to look at Sodom where the strange switching continues. Is it the two angles who are going to destroy the city or the LORD?
“There is a bewildering and continued juxtaposition of men, angels and the Lord. It is as if boundaries have disappeared. This passage puzzled Augustin, who wondered whether it describes an appearance of the pre-incarnate Christ, of all three persons of the Trinity, or of Angels. The point is that one God presents himself in a way that poses questions. As Wainwright comments, this “mysterious oscillation” aroused a great deal of discussion among the rabbis, although it was not until Justin Martyr in the second century that Christians began to consider the implications of the incident.” The Holy Trinity, Letham P24
I guess there is a way through by taking just one of the angles to be the LORD and having the LORD working through the two angles who destroy the city etc but to do so is to miss the obvious unusualness of the narrative. Well, I say unusual, but the same thing happens in a number of other places (Gideon, Moses and the burning bush, Jacob wrestling the angle of the LORD etc).
Hagar also sees and hears the angel of the LORD but says it is the LORD who spoke to her (and the implies she has seen God).
Gen 16:11-14 And the angel of the LORD said to her, “Behold, you are pregnant and shall bear a son. You shall call his name Ishmael, because the LORD has listened to your affliction. He shall be a wild donkey of a man, his hand against everyone and everyone’s hand against him, and he shall dwell over against all his kinsmen.”So she called the name of the LORD who spoke to her, “You are a God of seeing,” for she said, “Truly here I have seen him who looks after me.” Therefore the well was called Beer-lahai-roi; it lies between Kadesh and Bered. (ESV)
There are literally dozens of Trinitarian verses in the NT but here is a great one from the OT:
Is 48:16 Draw near to me, hear this:
from the beginning I have not spoken in secret,
from the time it came to be I have been there.”
And now the Lord GOD has sent me, and his Spirit.
NICOT says it’s the prophet speaking in the fourth line while it’s God in the first three. Calvin agreed. That may well be true but surely, like so much of OT prophecy, it is about Jesus. The phrase seems purposefully crafted to sit perfectly in his mouth. Like so much prophecy it has an immediate meaning and a messianic meaning.
I like to think of it in terms of clothes. To save money parents sometimes buy things for their children that are a little on the large size. The idea being that in a month or so their children will grow into them and so therefore get more use out of them. OT prophecy is a bit like that. It hangs like a baggy blazer around the immediate context but fits like a glove on Jesus.
Here’s another LORD/Jesus link in the OT where Yahweh talks about being valued at 30 shekels of silver:
Zech 11:13 Then the LORD said to me, “Throw it to the potter”–the lordly price at which I was priced by them. So I took the thirty pieces of silver and threw them into the house of the LORD, to the potter. (ESV)
Jesus was priced at 30 pieces of silver by Judas which, unless this is a massive coincidence, identifies Jesus with Jehovah.
Here is another match:
 The burden of the word of the LORD concerning Israel: Thus declares the LORD, who stretched out the heavens and founded the earth and formed the spirit of man within him….  “And I will pour out on the house of David and the inhabitants of Jerusalem a spirit of grace and pleas for mercy, so that, when they look on me, on him whom they have pierced, they shall mourn for him, as one mourns for an only child, and weep bitterly over him, as one weeps over a firstborn. (ESV) Zech 12:1,10
This is Yahweh speaking but its sounds a lot like what happened to Jesus. I don’t know if its there in the Hebrew (I have only jut started learning it) but the “me”/”him” language seems to speak of both unity and distinction of persons.
I’ll finish with a verse from the NT.
Jude 1:4 For certain people have crept in unnoticed who long ago were designated for this condemnation, ungodly people, who pervert the grace of our God into sensuality and deny our only Master and Lord, Jesus Christ. (ESV)
If Jesus is our only Lord and Master then who is Yahweh? There is often an “and” in these sort of verses as in “God and Jesus” but also a unity that identifies Jesus with Yahweh.
I finished the days teaching by quoting from Sherlock homes.
“When you have eliminated the impossible, whatever is left, however improbable, must be the truth”.
It’s a bit like that with the trinity:
1) There cannot be more than one God because Yahweh says “before me no other God was formed, nor any after me” (Is 43:10). But Jesus is so closely identified with Yahweh that we can rule out his not being God. It is in fact the very verses that affirm the oneness of God that rule out the option of Jesus being another God and leave only the option of him being God.
2) But Jesus also speaks to God, so there can’t be one God with two hats on talking to himself. We can rule that out. So what have we got left?
3) Half a God or a third of a God is no god at all, so each must be fully God.
Basically, I may not understand the trinity, but I can rule out everything else as impossible. The disciples, monotheistic Jews, had no problem relating to and writing about Jesus as God. The history of the Early church on this doctrine was basically people just ruling out heresies when they came along on the basis that they were impossible based on their experience and the apostolic testimony. What they were left with, however improbable, however mysterious, however it stretches our minds and goes beyond our fathoming out, must be the truth! The labelled they eventualy put on it is well chosen, having as it does a pointer to both the three-ness and unity of God; The trinity. Good call!