The Prophet (peace and blessings of Allaah be upon him) said:
“The likeness of a righteous companion and an evil companion is that of one who carries musk and one who works a bellows. With the one who carries musk, either he will give you some or you will buy from him or you will notice a pleasant fragrance from him. With the one who work a bellows, either he will burn your clothes or you will notice a foul odour from him.”
Narrated by al-Bukhaari, 5534; Muslim, 2628, from Abu Moosa al-Ash’ari, may Allaah be pleased with him).