Masechet Avot, Perek Aleph, Mishnah Zayin. The Mishnah says: Nittai HaArbeli Omer (Nittai HaArbeli says): Harchek Mishachen Ra (Distance yourself from a bad neighbor). Don’t live near a person who has wicked ways. Eventually, a person, when he’s around something so often, may learn from it. He may pick up some of these negative actions. Stay away from this person. This will also protect you from the harm that may happen to them because of their averot (transgressions)—the collateral damage. Everything within their vicinity does get harmed in some way. So stay away from a bad neighbor. Distance yourself from them.
Number two: Ve’al Titchaber LaRasha (Don’t befriend a wicked person). Have nothing to do with them. Even if you may think you’re joining them for a positive action, maybe you’ll join them to perform a mitzvah (positive action) together, or you’ll open a business with them and try to keep it professional, not personal. We say that automatically, a person is influenced by his surroundings as well and will become influenced by this wicked person. The rabbis bring down the mashal (parable) of somebody who walks into a tannery. A tannery is where they take animal hides and treat them in order to make them into leather. Even if you don’t buy anything with you, automatically you leave with the stench, with the smell of the animal hide. So when you’re around the rasha (wicked person), even if you don’t think you’ve done anything wrong or you don’t think you’re changing your actions, automatically you’re having had some influence on you without your control.
And lastly, don’t give up on seeing the punishment of the wicked people. Even if you see a wicked person who seemingly is enjoying his life and is successful, don’t say, “You know what? Maybe I’ll just make friends with him, and I’ll reap the benefits in the meantime.” You never know when Hashem is going to punish. You never know when issues are going to arise. Therefore, always stay away from this person, no matter what the situation is.