Don't count your chickens

[Alfie8]

Which novel is the source of the saying 'Don't count your chickens before they're hatched'?

[Quizmonster]

The words: 'Don't count your chickens before they are hatched' was considered a proverb as long ago as the 1500s, so presumably they were around for quite some time before that. That long predates anything which might be thought of as a 'novel', so I'm afraid no novel was their source.
There may well, of course, be a novel in which they feature importantly, but not as the origin.

[Hammond Egg]

The source isn't a novel but one of Aesop's fables, to which 'don't count your chickens . . . ' is the moral.