Hazrat Abu Musa (may Allah be pleased with him) narrated that the Prophet Muhammad (peace and blessings be upon him) said: The example of a good and a bad companion is like that of one who carries musk and one who blows the bellows (of a blacksmith). (The one who has musk and you are in his company) he will either give you some as a gift, or you will buy some from him, or (at the very least) you will enjoy its pleasant fragrance. And the bellows-blower will either burn your clothes (with the fire of the furnace), or you will get a foul, offensive smell from him.