It was narrated from Jabir bin 'Abdullah that:
a Bedouin pledged Islam to the Messenger of Allah, then the Bedouin was stricken with the fever in Al-Madinah. So he came to the Messenger of Allah and said: O Messenger of Allah, cancel my pledge, but he refused. Then he came to him again and said: Cancel my pledge, but he refused. Then he came to him again and said: Cancel my pledge, but he refused. Then the Bedouin left (Al-Madinah) and the Messenger of Allah sadi: Al-Madinah his like the bellows; it expels its dross and brightness its good.