Isaiah 37:21 - Ellicott's Commentary On The Whole Bible

Then Isaiah the son of Amoz... — According to the rectified chronology, the grand burst of prophecy which follows was the last of Isaiah’s recorded utterances. As such, it will be interesting to note any points of contact that present themselves either with his earlier prophecies or with the great prophetic poem (Isaiah 40-66) traditionally ascribed to him. The prayer of Hezekiah, if he was not present at its utterance, was reported to him, and in the name of Jehovah he was commissioned to reply to it.