Abu Musa reported: The Messenger of Allah, peace and blessings be upon him, said, “The parable of a good friend and a bad friend is that of a seller of musk and a blacksmith. The seller of musk will give you some perfume, you will buy some, or you will notice a good smell. As for the blacksmith, he will burn your clothes or you will notice a bad smell.”

Source: Sahih Bukhari 1995, Sahih Muslim 2628