They might have read this in some Prophets who are not in our canon, as Nathan or Esdras. That there was some prophecy to this purport is clear from what Philip says to Nathanael. “Him of whom Moses in the Law and the Prophets did write, Jesus of Nazareth.” [John 1:15] Hence the Christians were at first called Nazarenes, at Antioch their name was changed to that of ‘Christians.’
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).