Which book mentions Isaiah's prophecy?

Answer 1

More than any other gospel, the gospel of Matthew emphasises the supposed fulfilment in the New Testament of prophecies and prefigurement in the Old Testament. The author of Matthew's Gospel found more than one supposed prophecy in the Book of Isaiah, the most famous example of which is the claim that Isaiah 7:14 prophesied that a virgin would give birth. However, the Hebrew scriptures did not even contain those words - this is only to be found in the Septuagint, a flawed, early Greek translation of the Hebrew scriptures. The actual Hebrew text refers to "the young woman" and the the young woman in question did indeed bear a child a few verses later. The author of Matthew either did not know the Hebrew text, or believed that his intended audience would only check against the Septuagint, not the original text.