Let us look at the gospel of John. Here at the end of chapter 12, this is towards the end of Jesus' public ministry. And this is before the private ministry to the disciples. And verse 39...
39 For this reason they could not believe, for Isaiah said again,
40 “He has blinded their eyes and He hardened their heart, so that they would not see with their eyes and perceive with their heart, and be converted and I heal them.”
41 These things Isaiah said because he saw His glory, and he spoke of Him.
Now I'm sure you've read that before, but have you ever stopped and asked yourself the question.
"...Isaiah said because he saw his glory." In the context, it's only Jesus. So when did Isaiah see Jesus' glory? Well, we just had a quotation so where's the citation from? From Isaiah chapter 6. You know Isaiah chapter 6 I'm sure. It's about the prophets vision of God sitting upon His throne...
1 In the year of King Uzziah’s death I saw the Lord sitting on a throne, lofty and exalted, with the train of His robe filling the temple.
2 Seraphim stood above Him, each having six wings: with two he covered his face, and with two he covered his feet, and with two he flew.
3 And one called out to another and said,
“Holy, Holy, Holy, is the Lord of hosts,
The [a]whole earth is full of His glory.”
4 And the foundations of the thresholds trembled at the voice of him who called out, while the temple was filling with smoke.
5 Then I said,
“Woe is me, for I am ruined!
Because I am a man of unclean lips,
And I live among a people of unclean lips;
For my eyes have seen the King, the Lord of hosts.”
The quotation from Isaiah 6 is from verse 10...
10 Make the heart of this people “Render the hearts of this people insensitive,
Their ears dull,
And their eyes dim,
Otherwise they might see with their eyes,
Hear with their ears,
Understand with their hearts,
And return and be healed.”
So do you see what John is saying in John chapter 12? When he said, Isaiah said these things because he saw His glory and spoke of Him.
If you asked Isaiah... "Isaiah? Who did you see in Isaiah chapter 6?" Isaiah's response would have been, YHWY. YHWY was sitting upon His throne lofty and lifted up.
But if you asked John, "Who did Isaiah see?" Johns answer, is Jesus. The one sitting upon the throne, is Jesus.