What does 1 Samuel 24:13 mean?

Like people say, 'Evil comes from those who do evil.' So you can see I won't lay a hand on you. 1 Samuel 24:13 - Modern Text Bible

(David is quoting a common saying to make his point: people who do wrong are the ones who do harm, but he's not that kind of person. He's telling Saul he won't attack him.)