A group of people came to Madinah with the Prophet ﷺ at a time when illness was spreading there. The Prophet ﷺ forbade them from leaving until he gave them permission, but they departed without his consent. The Messenger of Allah ﷺ said, "Madinah is like a bellows. It expels its impurities just as a bellows expels the impurities of iron."
حدثنا حسين بن محمد حدثنا الفضيل يعني ابن سليمان حدثنا محمد بن أبي يحيى عن الحارث بن أبي يزيد
أن قوما قدموا المدينة مع النبي ﷺ وبها مرض فنهاهم النبي ﷺ أن يخرجوا حتى يأذن لهم فخرجوا بغير إذنه فقال رسول الله ﷺ إنما المدينة كالكير تنفي الخبث كما ينفي الكير خبث الحديد
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Its isnad is sahih. Husayn bin Muhammad here is Ibn Ayub Dhira, Fudayl bin Sulayman is Numayri, Muhammad bin Abu Yahya is Salami, and Harith bin Abu Yazid is the client of Hakam. All of them are trustworthy, and the hadith has previously appeared at 14872.