Mukhtasar Muslim

Sayyiduna Abu Musa (may Allah be pleased with him) narrates from the Noble Prophet (peace and blessings be upon him) that he said: The example of a good companion and a bad companion is like that of a musk seller and a blacksmith. The musk seller will either give you some as a gift, or you will buy some from him, or you will get a pleasant fragrance from him. As for the blacksmith, he will either burn your clothes, or you will have to smell a bad odor from him. (That is, the effects of good and bad companions are reflected upon a person.)