An Arabi pledged allegiance to the Messenger of Allah ﷺ accepting Islam, but then the Arabi was struck by a fever in Madinah. So he came to the Messenger of Allah ﷺ and said, "Messenger of Allah, release me from my pledge."The Messenger of Allah ﷺ refused. The man came to him again and said, "Release me from my pledge," and he refused. Then he came a third time and said, "Release me from my pledge," and again he refused. So the Arabi departed.The Messenger of Allah ﷺ then said, "Madinah is like a blacksmith's bellows. It drives out its impurities and leaves its good pure."
و حدثني يحيى عن مالك عن محمد بن المنكدر
أن أعرابيا بايع رسول الله ﷺ على الإسلام فأصاب الأعرابي وعك بالمدينة فأتى رسول الله ﷺ فقال يا رسول الله أقلني بيعتي فأبى رسول الله ﷺ ثم جاءه فقال أقلني بيعتي فأبى ثم جاءه فقال أقلني بيعتي فأبى فخرج الأعرابي فقال رسول الله ﷺ إنما المدينة كالكير تنفي خبثها وينصع طيبها