Abu Musa (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "The example of a good companion and a bad companion is like that of a musk seller and a blacksmith who blows the bellows. The musk seller may either give you some (musk) as a gift, or you may buy it from him, or at least you will get a pleasant fragrance from him. As for the one who blows the bellows, he may burn your clothes, or you will get a foul smell from him." Agreed upon.