It's funny that they go right to Isaiah 40. I personally love the Insight book's statement on that. Insight On The Scriptures is unintentionally hilarious at times.
Unity of Writership. Certain Bible critics in modern times have contended that the book of Isaiah was not all written by Isaiah. Some claim that chapters 40 through 66 were written by an unidentified person who lived about the time of the end of the Jews’ Babylonian exile. Other critics pare off additional portions of the book, theorizing that someone other than Isaiah must have written them. But the Bible itself does not agree with these contentions.
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Jesus Christ himself, when he read from “the scroll of the prophet Isaiah” at the synagogue in Nazareth, was reading fromIsaiah 61:1, 2.—Lu 4:17-19.
Furthermore, the Dead Sea Scroll of Isaiah (IQIsa, believed to have been copied toward the end of the second century B.C.E.) contains evidence that the copyist who penned it knew nothing of any supposed division in the prophecy at the close ofchapter 39. He began the 40th chapter on the last line of the column of writing that containschapter 39.