Sahih Bukhari Volume 3, Book 34, Hadith Number 314.

Narated By Abu Musa : Allah’s Apostle said, “The example of a good companion (who sits with you) in comparison with a bad one, is I like that of the musk seller and the blacksmith’s bellows (or furnace); from the first you would either buy musk or enjoy its good smell while the bellows would either burn your clothes or your house, or you get a bad nasty smell thereof.”