The prophet (saw) said "The example of a good companion and a bad one is the bearer of musk and the worker on the fires. A bearer of musk would give you some, you might buy some from him, or you might enjoy the fragrance of his musk. The worker on the fires, on the other hand, might spoil your clothes with sparks from his bellows, or you get a bad smell from him." (Sahih Bukhari and Muslim)