The good companion and the bad companion can be compared to a man who sells perfume and a blacksmith. When you visit the perfume seller he may give you a gift or you may purchase some musk from him and at the very least you leave with a sweet trace of his scent upon you. When you visit the blacksmith his flying sparks may burn your clothes and you will leave smelling of the smoke from his furnace.
—The Prophet Muḥammad
(Read on pg 97, Mohsen Shaker al-Bayoumi, Slaves of the All-Merciful. Ta-Ha Publishers. London: 2005.)