Abigail's quote proves her description because her description says she has an endless capacity for dissembling, which means she is deceiving. This reflects her character because she's manipulative with her relationships with other people. The quote was a perfect example because she threatens to slit all the girls throats and tells them all exactly what to say, but then she acts very different towards the adults.

John Proctors quote proves his description because he hates hypocrites and many people don't like him because he can expose their foolishness, he is a good man but the affair with Abigail has got too him and he regrets it after it happens. He makes it clear he doesn't want anything more with Abigail because he doesn't want a bad reputation because he cares about his image. The quote was him telling Abigail he's through with the affair.