In The Laws of Plato in book V, the Athenian stranger says the greatest penalty of evil doing is to become like evil doers and to have to hang out with them. We learn something the is brought in books of Musar that one tends to become like those he or she hangs around with.

Also a very interesting observation I found there: that the untrustworthy person ends up alone because eventually it becomes known that he can not be relied on to keep his word