Here is section IX of Walter Benjamin's "Theses on the Philosophy of History" in its entirety, together with a reproduction of the Paul Klee work that inspired it. Note that the German word Engel is masculine, which helps to explain why this potentially gender neutral being is rendered as a "he":
Mein Flügel ist zum Schwung bereit, ich kehrte gern zurück, denn blieb ich auch lebendige Zeit, ich håtte wenig Glück, -- Gerhard Scholem, "Gruß vom Angelus"
A Klee painting named "Angelus Novus" shows an angel looking as though he is about to move away from something he is fixedly contemplating. His eyes are staring, his mouth is open, his wings are spread. This is how one pictures the angel of history.His face is turned toward the past. Where we perceive a chain of events, he sees one single catastrophe which keeps piling wreckage upon wreckage and hurls it in front of his feet. The angel would like to stay, awaken the dead, and make whole what has been smashed. But a storm is blowing from Paradise; it has got caught in his wings with such violence that the angel can no longer close them. The storm irresistibly propels him into the future to which his back is turned, while the pile of debris before him grows skyward. This storm is what we call progress.
Paradise here is not a goal we can attain, but somewhere that will always be out of reach because it lies in the past. I like to think of the pile as the sort of place where the odd postcard, book, or snapshot rises to the top to catch the eye, like an autumn leaf swirling on a moody current.