Narrated Jabir bin `Abdullah: A bedouin gave the Pledge of allegiance to Allah's Apostle for Islam. Then the bedouin got fever at Medina, came to Allah's Apostle and said, O Allah's Apostle! Cancel my Pledge, But Allah's Apostle refused. Then he came to him (again) and said, O Allah's Apostle! Cancel my Pledge. But the Prophet refused Then he came to him (again) and said, O Allah's Apostle! Cancel my Pledge. But the Prophet refused. The bedouin finally went out (of Medina) whereupon Allah's Apostle said, Medina is like a pair of bellows (furnace): It expels its impurities and brightens and clears its good.