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.  

أَنَّ أَعْرَابِيًّا بَايَعَ رَسُولَ اللَّهِ ﷺ عَلَى الإِسْلاَمِ فَأَصَابَ الأَعْرَابِيَّ وَعَكٌ بِالْمَدِينَةِ فَجَاءَ الأَعْرَابِيُّ إِلَى رَسُولِ اللَّهِ ﷺ فَقَالَ يَا رَسُولَ اللَّهِ أَقِلْنِي بَيْعَتِي فَأَبَى ثُمَّ جَاءَهُ فَقَالَ أَقِلْنِي بَيْعَتِي فَأَبَى فَخَرَجَ الأَعْرَابِيُّ فَقَالَ رَسُولُ اللَّهِ ﷺ إِنَّمَا الْمَدِينَةُ كَالْكِيرِ تَنْفِي خَبَثَهَا وَتَنْصَعُ طَيِّبَهَا