From the poem (3rd verse) of the same name By Lord Byron in his Hebrew Melodies. Taken from the bible (2 Kings 18–19, Isaiah 36–37). This is in no way meant as political statement, rather an appreciation for an old poem fantasising a fictious event. Not a contentious comment by any means, since the actual events (ie the siege of Jerusalem) did not result in the destruction of the Assyrian army as described in the book of kings, rather Sennacherib withdrew his forces after receiving tribute from the Judeans.

Sidebar (sort of). There's over 120 figures in this render (barbecue time for my gpu). In case you can't read all the text properly (choice of dodgy fonts it reads:
For the Angel of Death spread his wings on the blast,
And breathed in the face of the foe as he passed;
And the eyes of the sleepers waxed deadly and chill,
And their hearts but once heaved, and for ever grew still!
Interesting sidebar Did you know Pam Poovey from Archer has the words tattooed on her back from her bare knuckle fighting days.
This is a nightmare poem to teach (from personal experience)...
Now I'm considering having a crack at the first verse