Harry Potter and the Goblet of Fire
How we cite our quotes:
Sirius and Snape were eyeing each other with the utmost loathing.
"I will settle, in the short term," said Dumbledore, with a bite of impatience in his voice, "for a lack of open hostility. You will shake hands. You are on the same side now. Time is short, and unless the few of us who know the truth stand united, there is no hope for any of us.
Very slowly – but still glaring at each other as though each wished the other nothing but ill – Sirius and Snape moved toward each other and shook hands. They let go extremely quickly.
"That will do to be going on with," said Dumbledore, stepping between them once more." (36.178-80)
The relationship between Sirius and Professor Snape is filled with unrelenting hatred: they've despised each other ever since they were kids, and they're simply unable to get over their mutual loathing. Even though they are working for the same overall goal, they can scarcely bear to look at each other, all these years later. Yet, they now have to work together. Yeah, this is going to work out well: we think that Professor Dumbledore is being overly optimistic about the symbolic value of a handshake.