“Snape replied pointedly, “I learned when not to talk from the master, Albus.”
“Cedric nodded to Snape. Snape knew the ghost didn’t like to talk to him. Something about a ghost talking to a painting seemed to disturb the boy. Nothing technically human on either end, Snape figured.”
“For a great master, everyone is a master, because he learns from everyone! For a great master, everything is a master, because he learns from everything!”
“Snape raised his wand and pointed it directly at Dumbledore."Avada Kedavra!”
“Another ten points from Gryffindor,” said Snape. “I would expect nothing more sophisticated from you, Ronald Weasley, the boy so solid he cannot Apparate half an inch across a room.”
“Shall I tell you the secret of the true scholar? It is this: every man I meet is my master in some point, and in that I learn of him.”