وَعَنْ جَابِرِ بْنِ عَبْدِ اللَّهِ: أَنَّ أَعْرَابِيًّا بَايَعَ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَأَصَابَ الْأَعْرَابِيَّ وَعَكٌ بِالْمَدِينَةِ فَأَتَى النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَقَالَ: يَا مُحَمَّدُ أَقِلْنِي بَيْعَتِي فَأَبَى رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ ثُمَّ جَاءَهُ فَقَالَ: أَقِلْنِي بَيْعَتِي فَأَبَى ثُمَّ جَاءَهُ فَقَالَ: أَقِلْنِي بَيْعَتِي فَأَبَى فَخَرَجَ الْأَعْرَابِيُّ فَقَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «إِنَّمَا الْمَدِينَةُ كَالْكِيرِ تَنْفِي خبثها وتنصع طيبها»

Jabir b. ‘Abdallah told of a desert Arab who had sworn allegiance to God’s messenger, but who, when he suffered from a bout of fever in Medina, came to the Prophet and said, "Cancel my oath of allegiance, Muhammad;” but God’s messenger refused. He came again with the same request and again he refused. He came once more with the same request, and when he again refused, the desert Arab went off. God’s messenger then said, "Medina is like bellows which drives away its impurity and purifies what is good in it.” Bukhari and Muslim.