One of the best texts to go to when dealing with the Jehovah’s Witnesses to prove the divinity of Christ is John 12:41, which states;
These things Isaiah said because he saw His glory, and he spoke of Him. (John 12:41, NASB)
John is clearly speaking about the Lord Jesus Christ in this verse and is applying the glory which Isaiah saw, to the second person of the Trinity. However, when one looks in the pages of their Bible, they may be a bit shocked to see that Isaiah 6 does not specifically refer to Isaiah “seeing” the glory of Yahweh. Note the text below from the NASB;
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 whole earth is full of His glory.” (Isa. 6:1-3, NASB)
It’s true that one could draw in inference from verse 3 of the text, where Isaiah states; “The whole earth is full of His glory.” However, that does not seem to be what the apostle John had in mind. In dealing with this issue, we must remember that the Scriptures at the time of the first century were the Greek Scriptures, or, the Greek Septuagint (LXX) and not the Hebrew Scriptures. When one goes to the LXX rendering of Isaiah 6:1-3, this is what is found;
And it happened in the year that King Ozias died that I saw the Lord sitting in a throne, lofty and raised up,and the house was full of his glory. And seraphin stood around him; the one had six wings and the one had six wings, and with two they covered their face, and with two they covered their feet, and with two they flew. And they cried out to one another and said; “Holy, holy, holy is the Lord Sabaoth; the whole earth is full of his glory.” (Isa. 6:1-3, New English Translation of the Septuagint, Oxford University Press, 2007)
Here, in the LXX rendering, Isaiah actually “saw” the glory of the Lord, “and the house was full of His glory.” The NET Bible provides some helpful textual notes on this verse (John 12:41) which state;
88tnGrk “his”; the referent (Christ) has been specified in the translation for clarity. The referent supplied here is “Christ” rather than “Jesus” because it involves what Isaiah saw. It is clear that the author presents Isaiah as having seen the preincarnate glory of Christ, which was the very revelation of the Father (see John 1:18; John 14:9).
snBecause he saw Christ’s glory. The glory which Isaiah saw in Isa 6:3 was the glory of Yahweh (typically rendered as “Lord” in the OT). Here John speaks of the prophet seeing the glory of Christ since in the next clause and spoke about him, “him” can hardly refer to Yahweh, but must refer to Christ. On the basis of statements like 1:14 in the prologue, the author probably put no great distinction between the two. Since the author presents Jesus as fully God (cf. John 1:1), it presents no problem to him to take words originally spoken by Isaiah of Yahweh himself and apply them to Jesus.
So, in short, John attributes Isaiah’s vision of Yahweh to none other than the Lord Jesus Christ. This comes as no surprise to the orthodox Christian and Trinitarian, who affirms the deity of Christ as the Second Person of the Trinity, co-equal, co-eternal and co-powerful. However, to the Jehovah’s Witnesses, this “should” be very disturbing. Why? Well first, it is direct testimony that Jesus is Jehovah. Second, the Witnesses failed to “cover their bases” when producing the New World Translation (NWT: a translation which has been documented to attempt to eliminate the deity of Christ). For instance, Isaiah 6:1-3 (the same text as cited above) reads;
In the year that King Uz·zi´ah died I, however, got to see Jehovah, sitting on a throne lofty and lifted up, and his skirts were filling the temple. 2Seraphs 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. 3And this one called to that one and said: “Holy, holy, holy is Jehovah of armies. The fullness of all the earth is his glory.” (Isa. 6:1-3, NWT)
The NWT clearly refers to this passage as Jehovah, and John 12:41 reads in the NWT; “Isaiah said these things because he saw his glory, and he spoke about him.” Hence, even the NWT refers to Jesus Christ as Jehovah. Now, the Witness may attempt to get out of this by claiming that the glory seen was Jehovah and not Jesus. meaning, they will say the “Him” in verse 41 is speaking about Jehovah alone. But, who is the context referring to? The very next verse proclaims;
Nevertheless many of the rulers believed in Him, but because of the Pharisees they were not confessing Him, for fear that they would be put out of the synagogue. (John 12:42, NASB).
The NWT rendering of this passage reads;
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. (John 12:42, NWT)
So, it must be asked, who is the “Him” that “many of the rulers” put their faith in verse 42? Well, it is the same “Him” as verse 41, Jesus Christ, who is being referred to as Jehovah; there is no contextual shift. It was the same “Him” that the people were putting their faith in verses 36-37, who again is the Lord Jesus Christ. Also, it was for believing in Jesus that one was kicked out of the synagogue (v. 42 – c.f. John 9:22, 16:2). Moreover, Jesus goes on to proclaim in verse 45 that to see Him is to see the Father. Why? because they are both Jehovah! Also see this helpful link from Dr. James R. White on this issue.