in Incidents in the Life of a Slave Girl by Harriet Jacobs . Where do you see evidence that quote " Slavery corrupts both the slaves and owners"

The above question is rather involved, and this is a short-answer forum. You are going to have an extremely hard time presenting your case of corruption if you haven't read the book, and if you don't understand the contect of the quotes or evidence you use.

The following sites should help you formulate your answer;

http://www.bowdoin.edu/~prael/projects/gsonnen/page2.html

http://www.enotes.com/incidents-life-slave-girl-text/chapter-ix-sketches-neighboring-slaveholders

http://www.wilkes.edu/Include/academics/kirby%20canon/Motherhood.pdf