John 12:37-41
37 But though he had done so many miracles before them, yet they believed not on him:
38 That the saying of Esaias the prophet might be fulfilled, which he spake, Lord, who hath believed our report? and to whom hath the arm of the Lord been revealed?
39 Therefore they could not believe, because that Esaias said again,
40 He hath blinded their eyes, and hardened their heart; that they should not see with their eyes, nor understand with their heart, and be converted, and I should heal them.
41 These things said Esaias, when he saw his glory, and spake of him.
Argument: John quotes Isaiah 53:1 and Isaiah 6:10 about Jesus, and says, "These things said Esaias, when he saw his glory, and spoke of him" (John 12:41). This refers to the glory of Yahweh spoken of in Isaiah 6:1-5, especially in the Septuagint, which additionally reads "glory" in Isaiah 6:1, and so John is identifying Jesus with Yahweh.
While it is possible that John is applying the passage about Yahweh to Jesus agentively (acting as God's agent), it is also possible that John is using "glory" in a more general sense, i.e., Isaiah, through his prophecies, saw the greatness of the Messiah, and truths about the Messiah, in a similar way Abraham can be said to have "rejoiced to see (Jesus's) day: and he saw it, and was glad" (John 8:56).
Further, John quotes Isaiah 53, which is part of a passage which speaks of the Messiah in these terms - "he shall be exalted and extolled, and be very high" (Isaiah 52:13), "he shall prolong his days, and the pleasure of the LORD shall prosper in his hand" (Isaiah 53:10), and, "Therefore will I divide him a portion with the great, and he shall divide the spoil with the strong" (Isaiah 53:12).
Additionally, the Septuagint, in this passage, specifically speaks of the Messiah's "glory":
Isaiah 52:13-14 (LXX)
13 Behold, my servant shall understand, and be exalted, and glorified exceedingly.
14 As many shall be amazed at thee, so shall thy face be without glory from men, and thy glory by the sons of men.
Therefore, the first passage that John quotes deals more directly with the glory and exaltation of the Messiah, and on that basis is probably a better candidate for what John would be referring to in John 12:41, though John using "glory" in the general sense seems to be the most likely interpretation.