This quote is found in the film version of To Kill a Mockingbird, but is actually not in Harper Lee's novel. In the film, Bob Ewell says this when he confronts Atticus in the street before Tom's trial. He is trying to intimidate Atticus beforehand, & making a poor attempt to connect with Atticus, adding "You got chillun of your own." Even though it was most assuredly Bob who raped and beat his daughter Mayella, he dares to challenge Atticus' methods of raising his children.
However, this scene was not written into the original novel. The filmmakers may have felt it would heighten the tension, & develop Bob's character more fully to have him confront Atticus before the trial, but no such addition was needed in the book.