I am quoting from the Watchtower's New World Transtion of the Holy Scriptures so that the Jehovah's Witnesses can not say I am using an incorrect translation. This is the official translation that the Jehovah's Witnesses accept word for word. I had to omit the special characters in the spelling of King Uzziah because they appear as garble on RHP.
Now from John Chapter 12:
Jesus spoke these things and went off and hid from them. But although he had performed so many signs before them, they were not putting faith in him, so that the word of Isaiah the prophet was fulfilled which he said: “Jehovah, who has put faith in the thing heard by us? And as for the arm of Jehovah, to whom has it been revealed?”
The reason why they were not able to believe is that again Isaiah said: “He has blinded their eyes and he has made their hearts hard, that they should not see with their eyes and get the thought with their hearts and turn around and I should heal them.”
Isaiah said these things because he saw his glory, and he spoke about him. All the same, many even of the rulers actually put faith in him, but because of the Pharisees they would not confess [him], in order not to be expelled from the synagogue; for they loved the glory of men more than even the glory of God.
However, Jesus cried out and said: “He that puts faith in me puts faith, not in me [only], but in him [also] that sent me; and he that beholds me beholds [also] him that sent me. I have come as a light into the world, in order that everyone putting faith in me may not remain in the darkness.
(John 12:36-46 NWT)
Notice in particular the part I have put in bold type. Here John is explaining why the Jews were unable to believe and put faith in Jesus. John refers to what Isaiah had said about the blinding of their eyes and the harding of their hearts so that they would not repent so Jesus should heal them. Then John goes on to say that Isaiah saw his glory and spoke about him (Jesus).
Below I have quoted what John was speaking about in scripture written by Isaiah.
In the year that King Uzziah died I, however, got to see Jehovah, sitting on a throne lofty and lifted up, and his skirts were filling the temple. Seraphs were standing above him. Each one had six wings. With two he kept his face covered, and with two he kept his feet covered, and with two he would fly about. And this one called to that one and said: “Holy, holy, holy is Jehovah of armies. The fullness of all the earth is his glory.” And the pivots of the thresholds began to quiver at the voice of the one calling, and the house itself gradually filled with smoke.
And I began to hear the voice of Jehovah saying: “Whom shall I send, and who will go for us?” And I proceeded to say: “Here I am! Send me.” And he went on to say: “Go, and you must say to this people, ‘Hear again and again, O men, but do not understand; and see again and again, but do not get any knowledge.’ Make the heart of this people unreceptive, and make their very ears unresponsive, and paste their very eyes together, that they may not see with their eyes and with their ears they may not hear, and that their own heart may not understand and that they may not actually turn back and get healing for themselves.”
(Isaiah 6:1-4,8-10 NWT)
John says Isaiah spoke these things because he saw Jesus (Yahshua), however, Isaiah says that he saw Jehovah (Yah---).
What is the explanation?
The Seraphs called out Holy! Holy! Holy! because they were in the presence of the Triune God, the Father, the Son, and the Holy Spirit. John can say Isaiah saw the glory of God and spoke of Him and be referring to Jesus, because Jesus (Yahshua) the Son is the glory of God that appeared in various ways to the prophets.
HalleluYah !!! Praise the Lord! Glory be to God! Holy! Holy! Holy!